Daniel has $25 to spend at the fair. if the admission to the fair is $4 and the rides cost $1.50 each , what is thw greatest number of rides daniel can go in ?

$25 is the total amount of money.
Admission is a constant, meaning that price will not vary and is fixed.
The rides each cost something so the price of rides will vary, unlike the constant (admission). 

Thus making x the number of rides, we have the equation:
25 = 4 + 1.5x.
We need to solve for x, but x must be a whole number so we will round down if the solution is not an integer.

1.5x = 21
Divide by 1.5 on both sides.
x=14

Daniel can go on 14 rides maximum.