What is the answer to 7x+2y=16 and -21x-6y=24 using the substituion method?

Answer 1

There's either a typo, or it's a trick question. Take a look at the equations.

7x+2y=16
-21x-6y=24

If you divide the 2nd by -3, you get

7x+2y = -8

There is no solution, since the left sides are the same, but the right is different. The lines are parallel.