Question

Given x+y=8, find y if x =3

Answer 1

X+y=8
(3)+y=8
⭐y=5
That would be the answer

Answer 2

Plug in x.

3+y=8

Subtract 3 on both sides. (do the inverse of addition; which is subtraction)

y=5

Check your answer.

3+5=8

8=8

That checks out! y is definitely 5.

I hope this helps!
~kaikers