A triangle has 180o and an isosceles triangle has two angles that are the same. As 70 is less than half, we have a couple of possible solutions to this. So one possible solution is 70-55-55. So the other possible solution is 70-70-40.
You can multiply 0.129 and 0.3 by 10 each to make it a little easier to see what to do.
0.129 / 0.3 = 1.29 / 3
Simple long division will take you to 0.43