A gardener planted 5 rows of vegetables. Each row has 3 pepper plants and s squash plants. The garden contains a total of 20 plants.
Which equation can be used to determine the number of squash plants that are in the garden?

3(5+s) = 20
(5x3) + (5xs) = 20
5(3+s) = 20
15 + 3s = 20
5 + 3 + s = 20