<<<if x=12, then x+2 = 16>>>> You mean if x=14, then x+2=16
I would do it a different way. Since the car has a 7 Min headstart, traveling at 60mph, you can figure the distance it is ahead of the truck. Then, with the truck overtaking the car, by 10mph, you can figure the time it would take, going 10mph to go this headstart distance.
The price of the belt was definitely omitted from the question, because with it being unknown, you cannot figure the price of the shirts.
math 5th grade
First off, 8 out of 9 customers ordered coffee, not 8/9 of a customer, as that doesn't make sense, (maybe one customer forgot his wallet, lol)customers are whole numbers and not fractional, use your brain. So: R+F=8 and, 3F=R, thus substituting 3F for R, 3F+F=8 or 4F=8 or ...
John mows lawn in 4 hrs or .25 lawn in 1 hr. Maria mows lawn in 3 hrs or .333 lawn in 1 hr. So in one hour they (combined) mow .25 + .333= .583 lawn(assuming they don't remow each others sections, lol) 1/.583 is 1.715hr John should just go home and let maria do it all.
Sally paints a house in four hrs or .25house per hour John paints house in 6 hrs or one in .166hrs If they worked together .25+.166= .416 house per hour or, 1/.416= 2.4 hrs per house