In case of two Poisson processes and one Poisson and the other 2-stages Erlang processes one can obtained explicit formulas of the joint and marginal distributions. But in case of two Ph -renewal processes it is difficult probably impossible to find the explicit formula`s of the joint and marginal distributions for the random variables TxN,xN and hN. Because of the analytical solution of the inverse matrix T is unsolvable problem, so the only transform functions were obtained. As its universal true that if one have transform function then the distribution function can be obtained. Therefore in this paper it`s considered to solve the inverse of the matrix T by putting some numerical values and using RIA (Rectangle Iterative Algorithm) and prove that if transform function is available then the distribution function should be obtained.