Question

3.
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$$\begin{cases} \\ \\ \\ y = 2x - 7 \\\\ \\ \\ \\ 4 + y = 12 \\end{cases}$$

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$$\begin{tabular}{|c|c|c|} \\hline step: & step 2: & check: \\\\ \\hline & & \\\\ \\hline \\end{tabular}$$

3
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Explanation:

Step1: Solve for $y$ in second equation

$4 + y = 12 \implies y = 12 - 4 = 8$

Step2: Substitute $y$ into first equation

$8 = 2x - 7 \implies 2x = 8 + 7 = 15 \implies x = \frac{15}{2} = 7.5$

Step3: Verify both equations

Substitute $x=7.5, y=8$ into $y=2x-7$: $2(7.5)-7 = 15-7=8$, which matches $y$.
Substitute $y=8$ into $4+y=12$: $4+8=12$, which is true.

Answer:

$x = \frac{15}{2}$ (or $7.5$), $y = 8$