WAEC 2023 · Paper 1 · Q12

Linear & simultaneous equations

One-third of the sum of two numbers is 12, and twice their difference is 12. Find the numbers.

Worked solution (try it first)

One-third of the sum is 12, so multiply by 3: $x + y = 36$ .
Twice the difference is 12, so divide by 2: $x - y = 6$ .
Add the equations: $2x = 42$ , so $x = 21$ .
Then $y = 36 - 21 = 15$ .
So the numbers are 21 and 15, option A.

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