How do you substitute 7x+2y=-19 and - x+2y=21

It's easier to use - x + 2y = 21

so make it all = to x

should come out to x = 2y - 21

now substitute what you just found = to x into the other equation

7 (2y - 21) + 2y = - 19

now distribute and simplify

14y - 147 + 2y = - 19

16 y = 128

y = 8

now substitute 8 for y in either equation

-x + 2 (8) = 21

-x = 5

x = - 5

Steps:

1. Take - x + 2y = 21

2. Add x on both sides

2y = x + 21

3. Divide everything by 2

Y = 1/2x + 10.5

4. Substitute the y in 7x + 2y = - 19 for 1/2x + 10.5

7x + 2 (1/2x + 10.5) = - 19

5. Multiply everything in parentheses

7x + x + 21 = - 19

8x + 21 = - 19

6. Subtract 21 on both sides

7. 8x=-40

8. Divide each side be 8

9. Your answer is

X=-5