Answer:
187 minutes
Step-by-step explanation:
Let the total bill be represented by b(x), where x is the number of minutes used.
Then b(x) = $3.00 + ($0.11/mile)x.
If David was billed $23.57, for how many minutes was he billed? Set this equation = to $23.57 and solve for x:
$23.57 = $3.00 + ($0.11/min)x, or
$20.57 = ($0.11/min)x.
To find x, divide both sides by $0.11/min:
x = $20.57 / ($0.11/min) = 187 minutes