Looking at Uranium the atomic number is 92 and so we can say the following:
U(235,92) + n(1,0) ----> 3n(1,0) + Kr(93,36) + x
in the following presentation the first number between paranthesis is the mass number the 2nd is the atomic number. We know that neutrons have a mass number of one ...
This solution explains how to find the atomic mass of a product of nuclear fission using the periodic table and equation-balancing methods.