Final answer:
David will pay $58.80 for 15 gallons of gas.
Step-by-step explanation:
To find out how much David will pay for 15 gallons, we need to use proportions. We know that he paid $27.44 for 7 gallons. So, the cost per gallon can be calculated as $27.44 divided by 7 = $3.92 per gallon. Now, we can find out how much David will pay for 15 gallons by multiplying the cost per gallon by the total number of gallons:
$3.92 x 15 = $58.80
Therefore, David will pay $58.80 for 15 gallons.