What is the value of x
2x+3y=45
x+y=10

Assuming this is a system of equations, here is how to find x. 

2x + 3y = 45
x + y = 10 

Multiply x + y = 10 by 2 so you are able to use the elimination method.

2x + 3y = 45
2x + 2y = 20

Subtract.

y = 25

Now that we've found y, we can plug it in to find x. 

x + 25 = 10

Subtract 25 from both sides.

x = -15