In any triangle, the angle values must add up to 180 degrees. If the third angle is 47 degrees and the remaining two angles are the same value, it would be really simple to solve.
First, subtract 47 from 180. You are left with 133. That is the sum of the two base angles combined.
In order to find the value for EACH base angle, divide 133 by 2. You are left with 66.5.
That is the answer! Both of the base angles are 66.5 degrees each.