MYP Maths: Linear Equations FAQ

You isolate the unknown by doing the same operation to both sides, in reverse order of operations — undo addition/subtraction first, then multiplication/division. Show every step: MYP criteria reward clear mathematical reasoning (Criterion A), not just a final answer, so a correct number with no working loses marks.

A linear equation is one where the unknown appears only to the power of 1 — no squares, no roots, no fractions with x in the denominator. Its graph is always a straight line, which is why linear equations connect directly to the gradient-intercept work (y = mx + c) you meet in the same unit.

Expand any brackets first, then clear fractions by multiplying every term by the lowest common denominator, and only then start isolating the unknown. Doing operations in the wrong order is the single most common reason students lose marks on otherwise correct working.

You use either substitution (rearrange one equation for a variable, then substitute into the other) or elimination (add or subtract equations to cancel a variable). Both find the point where two lines intersect — the x and y values that satisfy both equations at once.

If simplifying both sides leaves a false statement like 5 = 8, there's no solution — the lines are parallel and never meet. If you end up with a true statement like 3 = 3, there are infinite solutions — the two sides describe the exact same line.

The three I see every year: forgetting to apply an operation to both sides equally, mishandling negative signs when expanding brackets, and dividing only part of an expression instead of the whole side. Each one produces a wrong answer built on otherwise decent method — which is exactly why showing working matters.

Show every algebraic step in order, state your final answer clearly (e.g. 'x = 7'), and verify it by substituting back into the original equation. Under MYP Criterion A (Knowing and Understanding), examiners specifically look for organised, logical working — a jump from the question straight to the answer costs marks even if it's correct.

You solve them the same way, with one crucial exception: when you multiply or divide both sides by a negative number in an inequality, the inequality sign flips direction. Equations never have this rule because there's no direction to reverse — just equality.

Linear equations sit under the Algebra strand of MYP Mathematics, typically taught in MYP 4 and revisited with more complexity in MYP 5 as preparation for DP Mathematics AA or AI. According to the IB's MYP: From Principles into Practice guide, algebraic manipulation is a core skill assessed across all four MYP maths criteria, not isolated to one unit.

They're mainly assessed under Criterion A (Knowing and Understanding) for correct method and accuracy, and Criterion D (Applying mathematics in real-world contexts) when a question is set as a word problem. Both criteria are marked on 0-8 achievement level bands, and full marks require clear communication, not just a correct final value.

They're the direct foundation for solving systems of equations, straight-line graphs, and linear functions in both DP Mathematics: Analysis and Approaches and Mathematics: Applications and Interpretation. Students who are shaky on isolating variables in MYP 5 tend to struggle with the algebraic manipulation demanded in DP Paper 1, where no calculator is allowed.

Consistent, short practice beats occasional long sessions — 15-20 minutes of mixed linear equation problems two or three times a week embeds the method far better than a single two-hour cram before a test. Look for resources that show full worked solutions, not just final answers, so your child can spot exactly where their method went wrong.