Question

$\

$$\begin{cases} 7x - 12y = 19 \\\\ 4x + 3y = 31 \\end{cases}$$

$
$(?, \\ \\ \\ \\ \\ \\ \\ )$

Explanation:

Step1: Eliminate y variable

Multiply the second equation by 4:
$$4\times(4x + 3y) = 4\times31$$
$$16x + 12y = 124$$

Step2: Add to first equation

Add the new equation to $7x - 12y = 19$:
$$(7x - 12y) + (16x + 12y) = 19 + 124$$
$$23x = 143$$

Step3: Solve for x

Calculate x:
$$x = \frac{143}{23} = 7$$

Answer:

7