Question

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Answer 1

D. 7(10)+5(-6)=40
2(10)+4(-6)=-4

Answer 2

Using the substitution method:
equation 1: 7x + 5y = 40
equation 2: 2x + 4y = -4

dividing equation 2 by 2:
equation 2A: x + 2y = -2
making x the subject:
x = -2 - 2y

substituting that into equation 1:
7( -2 - 2y) + 5y = 40
-14 - 14y + 5y = 40
-14 - 9y = 40
-9y = 54
y = -6

substituting that into equation 2A:
x = -2 - 2(-6)
x = 10

∴ The answer is D (10, -6)