92 protons
143 neutrons.
Given the problem, you already know that the number of protons plus the number of neutrons will add up to 235. So use the periodic table to determine the number of protons. The atomic number of Uranium is 92, so there's 92 protons. So
92 + n = 235
n = 235 - 92 = 143
Therefore the number of neutrons is 143.
