Final answer:
Mark rented the bike for 3 hours.
Step-by-step explanation:
To find the number of hours Mark rented the bike, we can set up an equation.
Let the number of hours be represented by 'x'.
The cost of renting the bike can be expressed as $13 + $2x. Since Mark paid $19, we can set up the equation: $13 + $2x = $19.
To solve for 'x', we can subtract $13 from both sides of the equation to get $2x = $6. Then, divide both sides by $2: x = $3.
Therefore, Mark rented the bike for 3 hours.