Question 12

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waecmaths question: 

Given that $2x+y=7$and $3x-2y=3$, by now much is 7x greater than 10 

Option A: 

1

Option B: 

3

Option C: 

7

Option D: 

17

waecmaths solution: 

$\begin{align}  & 2x+y=7---(i) \\ & 3x-2y=3---(ii) \\ & \text{From }(i)\text{ }y=7-2x \\ & \text{Substitute }7-2x\text{ for }x\text{ in }(ii) \\ & 3x-2(7-2x)=3 \\ & 3x-14+4x=3 \\ & 7x-14=3 \\ & 7x=17 \\ & x=\tfrac{17}{7} \\ & \therefore (7\times \tfrac{17}{7})-10=7 \\\end{align}$

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