At each step, the quotient term is the ratio of the leading dividend term to the leading divisor term. The first quotient term, for example, is ...
(4x^4)/(x^2) = 4x^2
The quotient term found this way is multiplied by the divisor and subtracted from the dividend. The difference is the new dividend and the process repeats.
You're done when the degree of the dividend is less than the degree of the divisor. This remainder can be expressed as a fraction with the divisor as the denominator.
So look at it as a normal rectangle with just four sides. AB is 7.5, which is one side. And now to get the other side just add BC and DE together to complete the side. It would be 2.5 + 1.25= 3.75. And to get the perimeter just add 3.75+3.75+7.5+7.5. I hope this makes sense.