−x+3y=−15, 3x+3y=21 elimination

x= 9  y= -2

Step-by-step explanation:

Multiply the second equation by -1, then add the equations together.

(−x+3y=−15)

−1(3x+3y=21)

Becomes:

−x+3y=−15

−3x−3y=−21

Add these equations to eliminate y:

−4x=−36

Then solve−4x=−36for x:

−4x=−36

(Divide both sides by -4)

x=9

Substitute9forxin−x+3y=−15:

−9+3y=−15

3y−9=−15(Simplify both sides of the equation)

3y−9+9=−15+9(Add 9 to both sides)

3y=−6

(divide both sides by 3)

y= -2

x= - 6/7, y= - 129/12

Explanation:

use the addition/elimination method to solve for x. then sub in and test then lastly, multiply everything by 7 to eliminate the fraction