This is classic right triangle trig. Side a, our unknown, is adjacent to angle C which is a given. You always have to use a given angle and side to find a missing side, so we have to figure out how the two givens are related to our unknown. Side a is adjacent to angle C, and we are also given the hypotenuse. We know side a is not the hypotenuse since the hypotenuse is ALWAYS the side across from the 90 degree angle. The tan ratio of angle C will give us a way to have only one unknown.
Add all the numbers together, and divide your total by the number of value there (in this case, 7). The nearest tenth is to one place after the decimal.
