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WAEC Mathematics 2018 Paper

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Question : 9

Total: 50

If y + 2x = 4 and y - 3x = -1, find the value of (x + y)

3
2
1
-1

Solution:

Concept:

Solving a pair of linear equations by elimination.

Explanation:

Given equations:

y + 2x = 4

...(1)

y - 3x = -1

...(2)

Subtract equation (2) from equation (1):

(y + 2x) - (y - 3x) = 4 - (-1)

y + 2x - y + 3x = 4 + 1

5x = 5

x = \frac{5}{5} = 1

Substitute

x = 1

into equation (1):

y + 2(1) = 4

y + 2 = 4

y = 4 - 2 = 2

Therefore,

x + y = 1 + 2 = 3

Answer:

3

Option A.

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