The cost he will pay for 10 rides will be $70 and for r rides will be .
Step-by-step explanation:
The price of admission into the park is $20.The price for each ride is $5David takes 10 rides,So, the cost he will pay if he took 10 rides will be,If he had r rides,So, the cost he will pay if he took r rides will be,Therefore, the cost he will pay for 10 rides will be $70 and for r rides will be.
