A group of 140 tourists are going on a tour. The tour guide rents 15 van. Each van hold 9 tourist

The tour guide should have rented 16 vans to accommodate the group of 140 tourists.

We multiply the number of vans to the number of tourists it can hold.

15 * 9 = 135 tourists

Out of the 140 tourists, only 135 can be accommodated by the 15 vans rented leaving 5 tourists with no ride.

140 - 135 = 5 tourists

Had the tour guide rented 16 vans, everyone would have a ride, leaving 4 extra seats unoccupied.

16 * 9 = 144 tourists capable of being seated

144 - 140 (actual number of tourists) = 4 extra seats available.