Let us suppose number of rides is x.One ride costs $0.50.
Cost of x rides is 0.50x. The carnival charges is $5. Alex has $15 to spend .
Number of rides at most Alex can have can be given by the inequality:
0.50x+5≤ 15
To solve for x we subtract 5 both sides
0.50x≤ 15-5
0.50x≤ 10
Dividing both sides by 0.50 we have :
x≤ 20
Number of rides at most Alex can have is 20.