Modeling functions

Question

Suppose you run along a rectangular field. You run 8 miles per hour along the long sides and 5 miles per hour along the short sides.  (a) Determine an equation that describes the total time, T, that it takes you to run around the field as a function of its long side, L, and its short side, W. Use upper case letters. (b) Suppose it takes you 10 minutes to run around the entire field. If the field's short side is 2/3 its long side, determine the exact length of the long side of the field.

Answer 1

(a)

T = D / R

T = [2L / 8] + [2W / 5}

(b)

10 = [2L / 8] + [2(2/3)L / 5}

Can you solve for L and answer?