Question

1. \

$$\begin{cases}x = 4y + 7\\\\-10x + 9y = -70\\end{cases}$$

Explanation:

Step1: Substitute $x=4y+7$ into 2nd equation

$-10(4y+7)+9y=-70$

Step2: Expand and simplify left side

$-40y-70+9y=-70$
$-31y-70=-70$

Step3: Solve for $y$

$-31y=-70+70$
$-31y=0$
$y=0$

Step4: Substitute $y=0$ into $x=4y+7$

$x=4(0)+7$
$x=7$

Answer:

$x=7$, $y=0$