Advanced Math practice question

Answer: 10

x² − y² = (x − y)(x + y). So 40 = 4(x + y), giving x + y = 10. (Here x = 7 and y = 3.)

Common wrong answers

If you answered 36

36 is 40 − 4, subtracting instead of using the factored form (x − y)(x + y).

If you answered 44

44 is 40 + 4. The relationship is multiplicative: 4 × (x + y) = 40.

If you answered 160

160 is 40 × 4, multiplying instead of dividing.

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