Question

7x + 10y = 60
7x - 2y = 240
if (x, y) satisfies the given system of equations, what is the value of x ?

Explanation:

Step1: Subtract equations to eliminate $x$

$$(7x + 10y) - (7x - 2y) = 60 - 240$$
$$7x + 10y -7x +2y = -180$$
$$12y = -180$$

Step2: Solve for $y$

$$y = \frac{-180}{12} = -15$$

Step3: Substitute $y=-15$ into first equation

$$7x + 10(-15) = 60$$
$$7x - 150 = 60$$

Step4: Solve for $x$

$$7x = 60 + 150 = 210$$
$$x = \frac{210}{7} = 30$$

Answer:

$30$