System of equations

Question

Car Rentals rents cars and trucks for $25 and $30 dollars a day respectively. Last Tuesday, they rented all but 7 rental vehicles and reported $195 in lost rent. How many trucks were not rented last Tuesday?

Answer 1

if the number of trucks not rented is 7 and zero cars,then the loss would be 30*7 ie 210.

if no. of trucks not rented is 6 and no of cars not rented is 1 then the loss is 6*30+1*25=205

doing like this you will conclude that if 4 trucks and 3 cars are not rented ,then the loss would be 195 

 

hence 4 trucks are not rented