If the perimeter of a triangle is 7x + 13, and two sides measure -6x + 12 and 5x – 5. Find the missing side.

How to do this , and can some one explain

If, while training for a marathon, you ran 60 miles in 2/3 months, how many miles did you run each month? (assume you ran the same amount each month) write your answer as a whole number, proper fraction, or mixed number in simplest form. you ran __ miles each month.

Someone me what is the area of this figure? 18m 18m 8m 16m