Question

Solve x-y=3 and x+y=5

Answer 1

well.. have you covered system of equations yet?

Answer 2

Well, what two numbers can be subtracted and get the difference of 3, and also be added together to get the sum of 5?

Answer 3

You can always try plugging in numbers :)

Answer 4

I need to know where I need to add y-3 to both side of equation

Answer 5

You can solve this by solving for x in terms of y and then substituting that in order to solve for y.
Let's solve for x.
x+y=5
-y -y ~ Subtract y from both sides.
x=5-y ~ Now plug this in to the first equation.
(5-y)-y=3 ~ Simplify
5-y-y=3
5-2y=3 ~ Subtract 5 from both sides.
-2y=3-5
-2y=-2
y=1

I think you can do the rest! :)