Question

Brandon earns $6 for every shirt he sells. Which equation could Brandon used to determine the amount of money he earns (E) for any number of shirts (s) he sells

Answer 1

Simple,

since he has no money to begin with just write your equation..

E=6s

Which  basically means, if he sells 1 shirt:

E=6(1)
E=$6

If he sells 2 shirts:

E=6(2)
E=$12

And so on and so forth, thus, your equation is E=6s.