Answer:
12 sides
Explanation:
If the three equal angles add to 90, this means each of those angles must by 30 degrees.
Next, we can use the theorem that the sum of the exterior angles adds to 360 (this is true for any polygon). So, as the exterior angles are all equal to 30, we just work out 360 ÷ 30 = 12.
So the polygon has 12 angles, and therefore 12 sides also.