-1/3x-4/3y=2
1/3x-2/3y=4
First realize that the coefficient of x is -1/3 and 1/3 which can be eliminated with addition
Adding the two equations together gets
-6/3y=6
Simplify
-2y=6
y=-3
Substitute back into original equation
1/3x-2/3(-3)=4
1/3x+2=4
1/3x=2
x=6
Answer
x=6, y=-3
Check answer
-1/3(6)-4/3(-3) =?= 2
-2+4=2
2=2
Done!
You get everything you need from factoring the last expression:

The left side is a difference of squares, and we get another difference of squares upon factoring. We end up with

Plug in everything you know and solve for
:

There are 18 in Nevada.
Multiply 55% by 40, and you get the amount for California. (Which is 22.)
Subtract 40 by 22, and you get 18.
Hope this helps!