i dont know how to solve: x+y=21 and 2x=33+y

Answer 1

First of all, when you refer to yourself as the subject of a sentence, you use a capital letter I!

x+y=21

2x=33+y

From the first equation: y=21-x

Substitute into the 2nd equation:

2x = 33 + 21 - x

3x=54

You take it from here.