Now what you want to do is 21 + (-3). Since this is the same as saying 21 - 3, the answer is 18. Therefore, the answer is 18°F.
First you need to know that the internal angles of a triangle always equals 180°. Therefore:
15+45= 90°
Then since the angles should equal 180, you do:
180-90=90
So the missing angle equals 90°
Maybe, the price went down $20 eight times?
