Question

How would I solve x+2y=20, and x-y=16

Answer 1

well, is a system of equations
take a peek at the 2nd equation
x-y = 16

can you solve that for "x", what would it look like?

Answer 2

Wouldn't you start out with x-y=16, then convert it to x=-16+y?

Answer 3

well, yes, but what you have there is 16, not -16, so it'd be
x-y = 16
x = 16 +y

Answer 4

so we have
x+2y=20
x-y=16

and from solving for "x" on the 2nd equation, we now know that
x = 16 +y

now if I were to rewrite the 1st equation, with x = 16+y in mind, it'd be

\(\color{blue}{x}\) + 2y = 20
OR
\(\color{blue}{(16+y)}\) + 2y = 20

16 + y + 2y = 20

so now just solve for "y", what would that give you for "y"?