1. The problem statement, all variables and given/known data A steel pipe is 200mm internal diameter and 20mm thick. Calculate the safe internal pressure if the allowable stress is not to exceed 140Mpa. 2. Relevant equations σr = A-B/r^2 and σtheta = A+B/r^2 3. The attempt at a solution Right so, I've got two equations..... (eq1)140MPa =A+B/0.1^2 and (eq2)0 = A-B/0.12^2 I need help getting A and B. Answers (A=57.38)and (B=0.826) I know I need to use simultaneous equations. Could someone please give me a step by step solution as I'm stuck. I have so far done -(eq2)+(eq1) to cancel out A. and got ...140MPa = B/0.1^2 + B/0.12^2 I'm not sure what to do next to get B.