Step 1: All angles in a triangle must add up to 180! Therefore, in the upper triangle, add up the two you know 85+35=120 so the missing angle is 60.
Step 2: Bottom triangle. Your new angle above (60) is the pair of the opposite angle - so it too is 60. So now you know 2 of the 3 angles: 60+64=124 Subtract that from 180 and you get 56...which is the answer for ?