Your food bill at a restaurant is $30. you leave a 20% tip. the sales tax is 6%. what is the total cost of the meal?

The total cost of the meal is $37.80

Given:
Food bill = $30
tip = 20%
sales tax = 6%

Tip and sales tax must be based on the food bill.

Tip = $30 x 20% = $6
Sales Tax = $30 x 6% = $1.80

Food bill :   30.00
Tip               6.00
Sales tax     1.80
Total cost 37.80

So, if your food bill is 30$, and you want to leave a 20% tip, plus the sales tax of 6%, the total cost of the meal would be 37.8 $.
20% out of 30 = 6 (20% = 0.2; 30 * 0.2 = 6).
And 6% out of 30 = 1.8 (6% = 0.06; 30 * 0.06 = 1.8)
30 + 6 + 1.8 = 37.8