Finding the value of X for two Supplementary Angles

suppose angles A and B are supplementary angles. Also suppose the measure of angle A is (2x -30)*degrees* and the measure of angle B is (2/3X + 15)*degrees*.

Find the value of X. give an exact decimal answer answer.

ok what I did was take angle A + B = 180, and solve for the X value. I had to combine the two X values into one ... then isolate X on one side of the equal sign.

my answer was X= 435/8 which in decimal form is 54.375.

was this correct?