Who am I?
What is an angle whose degree measure is exactly 90?
right angle
What is a shape which sides add up to 180 degrees?
triangle
What is an angle whose degrees measure is exactly 180 degrees?
straight angle
15 + x = 90
75
What is a shape with 360 degrees?
circle
5x + 70 = 90
x = 4
7x + 110 = 180
x = 10