Solve 7x+2y=8, -5x-2y=-12 by elimination/addition

(-2, 11) That is, x = -2 and y = 11

Step-by-step explanation: We have a pair of simultaneous equations and since none of the variables has a coefficient of 1, we shall solve by use of the elimination method. The equations are

7x + 2y = 8 ———(1)

-5x - 2y = -12 ——(2)

The coefficients of the y variable in both equations is 2 in either case. So straight away, we add both equations together. (This is because of the negative sign in one the coefficients of y).

Adding both equations results in;

(7x + -5x) +(2y + -2y) = (8 + -12)

2x = -4

Divide both sides of the equation by 2

x = -2

Having calculated x, we now substitute for the value of x into equation (1)

7x + 2y = 8

7(-2) + 2y = 8

-14 + 2y = 8

Add 14 to both sides of the equation

2y = 22

Divide both sides of the equation by 2

y = 11

Therefore, x = -2 and y = 11

8(-10x+3.5y-7)

8×-10x + 8×3.5y + 8×-7

-80x + 28y - 56

therefore

-80x+28y-56 is the correct answer