Solve the system by substitution.
y = -2x - 7
9x - 10y = 12
First, let's solve the first equation for y:
y = -2x - 7
Now, substitute this value of y into the second equation:
9x - 10(-2x - 7) = 12
Simplify:
9x + 20x + 70 = 12
Combine like terms:
29x + 70 = 12
Subtract 70 from both sides:
29x = -58
Divide both sides by 29:
x = -2
Now, substitute this value of x back into the first equation to find y:
y = -2(-2) - 7
y = 4 - 7
y = -3
So, the solution is x = -2, y = -3.