you would need to multiply 27 by 2, to get the both sides or the tennis court, then you would subtract what you got from 210 in order to get the side lengths, divide that by 2 so u can get what each side is = 2
27 * 2 = 54
210 - 54 = 156
156/ 2 = 78
the side lengths of the court are 78 feet each