Assuming "d" is equal to the dollars Jacob earned and h= hours, you start by setting the equations equal to each other, since both are equal to "d."
15h=10h+20
Subtract 10h from both sides (to combine like terms) so the equation becomes:
5h=20
Divide 5 from both sides, to isolate "d" :
h=4
The number of hours Jacob worked is 4, as the equation above shows. To find the amount of money Jacob made, substitute 4 as "h" into the two original equations: