The answer is 15.9 centimeters. If you work backward with the formula 2pir = circumphrence, you get diameter *pi = 50. To find diameter, you divide 50 by pi and the answer is 15.9 centimeters.
I'm assuming you meant w^3 (w to the third power). In that case, you would just add 34 + 13 + 11 - 18 because they are all like terms (coefficients of w^3).
