We need to figure out the amount of tip he will be paying. So let's multiply the cost of his meal by the percent of his tax.
Let's convert 10% into a decimal, which we can easily do by moving the decimal point to places to the left.
10% = .1
Now, multiply .1 by 36.
36 * .1 = 3.6
To get Christopher's total bill, let's add the tip to the cost of his meal.
36 + 3.6 = 39.6
Christopher's breakfast costs $39.6 including tip.
