How do you solve y=2x+9 and y=9x +10 using substitution?

1 Answer
Apr 26, 2018

x = -1/7 and y = 8 5/7

Explanation:

Take one y value and substitute it as the y value in the other equation.

Let's use y = 2x + 9 to substitute in the other equation

2x + 9 = 9x + 10

Subtract 2x from both sides, then subtract 10 from both sides.

9 = 7x + 10
-1 = 7x

Divide both sides by 7

-1/7 = x

Now apply your new x value to the first equation, y = 2x + 9

y = (2*-1/7) + 9
y = -2/7 + 9
y = 8 5/7