Question

Find the solution of the system of equations. minus, 5, x, plus, 7, y, equals, 40 −5x+7y= 40 10, x, plus, 7, y, equals, 25 10x+7y= 25

Answer 1

For this system of equations, it is best to first solve an equation for one of the variables and plug that into the second equation.

-5x + 7y = 40 --> solve for x is easiest

1.4y - 8 = x --> plug x into second equation to find y

10x + 7y = 25

10(1.4y - 8) + 7y = 25

21y = 105

y = 5 --> plug into first equation to find x

-5x + 7y = 40

-5x + 5(5) = 40

x = -3

Step-by-step explanation:

-5x + 7y = 40 --> solve for x is easiest

+5x +5x

7y = 5x + 40

-40 -40

7y - 40 = 5x

divide by 5

1.4y - 8 = x --> plug x in for the second equation to solve for y

10x + 7y = 25

10(1.4y - 8) + 7y = 25

14y - 80 +7y = 25

+80 +80

21y = 105

y = 5 --> plug y value in to first equation (or second) to solve for x

-5x + 5y = 40

-5x + 5(5) = 40

-25 -25

-5x = 15

divide by -5

x = -3