Answer:
$39
Explanation:
To calculate the total cost of his meal, add the subtotal ($30), the tax on subtotal ($30 X 10%) and the tip ($30 X 20%).
Convert all percentages to decimals to multiply.
Finding tax:
10% = 0.1
Tax = $30 X 0.1 = $3
Finding tip:
20% = 0.2
Tip = $30 X 0.2 = $6
Subtotal + Tax + Tip
= $30 + $3 + $6
= $39
The total cost of his meal was $39.