Answer:
x = 4
Step-by-step explanation:
An equilateral triangle means that all three sides are equal. All triangles have an inner angle measure of 180 degrees. Divide 180 by 3 to find out a singular angle's measure. You end up with : 10x + 20 = 60. In order to isolate the 10x, subtract 20 from both sides. This gives you 10x = 40. Thus, x = 4.
