What are the steps to solve d=1/e + 1/f for e ?

Solve for e

d = 1/e + 1/f

Move 1/f to the left side of the = sign

d - 1/f = 1/e

Multiply each side by e

e(d - 1/f) =  e(1/e)

e(d - 1/f) = 1

Divide out (d - 1/f)

e(d - 1/f) / (d - 1/f) = 1 / (d - 1/f)

e = 1 / (d - 1/f)

to find the total number of combinations, multiply the quantity of each item by each other:

2 pairs of shoes x 3 pairs of shorts = 6 different combinations.