Ineed finding the perimeter of a rectangle

How do i work this problem out using the equation a=pe^rt

Compare the subtraction problems 6/8 - 5/8 = 1/8 and 6/9 - 7/9 = 1/9 why is the answer to the first problem positive and the answer to the second problem negative

5,600 x 10^3 = a) 560 b) 5,000,600 c) 5,600,000 d) 56,000