Answer: $25.41
Convert the percentage into a decimal, and then multiply that decimal by the total price to find the tip. Subtract the tip amount from the total price to find the price before the tip.
15 ÷ 100 = 0.15
15% of 29.90 = 0.15 · 29.90 = 4.48500 ≅ $4.49
$29.90 - $4.49 = $25.41
∴ the price before tip, b, of Mr. Johnson's lunch is $25.41.
