So first we write out their respective charges A=65+30x (x=hours of A) B=30+47.5y (x= hours of B)
we want to know when A and B are equal so just set them to be equal
65+30x=30+47.5x subtract 30 from both sides 35+30x=47.5x multiplyboth sides by 2 to get rid of the nasty decimal 70+60x=95x subtract 60x from both sides 70=35x divide both sides by 35 2=x they must work 2 hours for them to be equal