How to solve this problem by elimination 3x+y=17 4x+2y=20

1st you have to find what x, and y is
2nd re write the problem 
3rd solve it 

For elimination, you need to eliminate one of the variables by subtrating the two equations.
To do that, you need to multiply the equation 3x+y=17 by 2, which becomes 6x + 2y = 34.

Now you can subtract, but also multiply 6x+2y=34 by -1 so you can subtract:
4x + 2y = 20
-6x - 2y = -34

-2x + 0 = -14
x = 7

Now that you know x=7, plug it back in to one of the original equations to solve for y.
4x + 2y = 20
4(7) + 2y = 20
28 + 2y = 20
2y = -8
y = -4