this works because to find the middle of two numbers (in this explanation 10 and 20), you have to subtract the larger one from the smaller one (20 - 10 = 10) and take your sum and divide it by two (10 ÷ 2 = 5) and then add it back to the smaller number (5 + 10 = 15 = 1/2 the midpoint of 10 and 20)
Step-by-step explanation: a triangle has a total of 180 degrees, and the number of sides determine the number of angles it has. in this case, it's an equilateral triangle. 180/3 = 60. all triangles have 3 sides if you didn't know that ;)
