well, the sum of all internal angles in a triangle, isosceles or whatever else, is always 180°, so the sum of all those three folks, will be 180 then
so.. hmmm let's say the smallest angle is "a" units
twice that is, 2*a, or 2a
25 larger than that? is well 2a + 25
so... the other two twin angles, are 2a+25 each
thus a + (2a + 25) + (2a + 25) = 180
solve for "a" to find the smalles one
what about the twins? well, each is 2a + 25