In a parking lot some cars have 1 spare tire and others have no spare tires all together there are 43 tires and 9 cars how many cars have a spare tire?

Well, every car that I know of has 4 tires, so we multiply 9 by 4 to get 36 tires on the cars. We can ignore those tires as they are not spares.

So we are left with 7 tires (43 - 36 = 7) to be spares for 9 cars. Since some cars only have 1 and some have 0, those 7 tires go to 7 cars.

This means 7 cars have a spare tire, and 2 do not.