Math final kicking my could someone ?

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

What is the ratio of the length of an object in yards to the length of the same object in miles?

Isabel graphed the following system of equations. 2x – y = 6 y = -3x + 4 she came up with the solution (2,-2). what were the 3 steps she did to get that solution? (make sure they are in the correct order)