Recall two important facts:
- An isosceles triangle always has two identical angles
- The interior angles always add up to 180 degrees
Armed with this info, we can set up two different equations to solve for x, depending on which angle we treat as being one of the pair of identical angles.
If we assume that the identical angles are x, then:
180 = 2x + x + 10
170 = 3x
56[tex]\frac{2}{3}[/tex] = x
Alternately, we can assume that the identical angles are x+10. In this case:
180 = 2(x + 10) + x
180 = 2x + 20 + x
160 = 3x
53[tex]\frac{1}{3}[/tex] = x
