If we know that x = -5y + 36 The second line says that 5x + 5y = 0 We can substiute the value of x from the first line into the second line.
So it becomes 5 ( -5y+36) + 5y = 0 Distribute the 5 over the parentheses -25y + 180 +5y = 0 Then we can add things that are alike; so that means we can add the y values -20y + 180 = 0 Then add 20y to both sides of the equation 180 = 20y Then you divide by 20. You get 9 = y! Now that you have the value of y, you can put it back into the intial question. 5x+5y = 0 5x + 5(9) = 0 5x + 45 = 0 5x = -45 x = -9
