Solving+by+Substitution

5b. Here are examples of problems where the substitution method is used:

1) 3y-2x=11 y=9-2x

3(9 - 2x) - 2x = 11

(27 - 6x) - 2x = 11 27 - 8x = 11 -8x = -16 x = 2

Now you must plug in the x-value to find the y-value:

y = 9 - 2(2) y = 9 - 4 y = 5

The final answer would be (2,5)

2) 2x-3y=23 y=-5x=15

First you plug in the y= into the first equation: 2x-3(-5x+15)=23 2x+15x-45=23 17x=68 x=4

Then you must solve for the y-intercept: 5(4)=y=15 20+y=15 y=-5

The final answer is: (4,-5)