If i costs $5 per hour for a surfboard plus an initial payment of $20. for how many hours can i rent a surfboard if i have $90

Okay so take away $20 from your $90 you get $70. Divide $70 by $5 per hour and you get to rent a surfboard for 14 hours.

An equation to solve that problem can be
5x+20=90. X represents the hour/s.

You'd first use the subtraction property of equality and subtract 20 from both sides to get 5x=70. Then, you use the division property of equality and divide both sides by 5 to isolate the variable. You'd then get x=14

You'd be able to rent the surfboard for 14 hours

We need more info then that