9. Solve the system of equations using substitution.

y = 2x - 10

y = 4x - 8

Since they're both in standard form and they both say that y is equal to something, you just have to set them up with one another

2x-10=4x-8

Subtract 2x

-10=2x-8

Add 8

-2=2x

Divide by 2

-1=x

x=-1

Check it by inserting it

2 (-1) - 10=4 (-1) - 8

-2-10=-4-8

-12=-12

So x=-1 is the answer