Question

Use substitution to solve the system.
−5x - 3y = 21
x = 3y - 9

Answer 1

Alright, so first, plug in the second equations for x into the first equations like so:
-5(3y - 9) - 3y = 21.
Then the -5 into the parenthesis and solve.
-15y + 40 - 3y = 21
Then do the rest.

Answer 2

Once you find y, plug it in to one of the equations so you can solve for x.

Answer 3

Thank you