linear equations

Question

You go to a restaurant with a $20 bill to spend. You know that you'll pay 9% in sales tax and
you want to leave your waitress with at least a 15% tip. What is the most expensive meal that
you can eat?

Answer 1

Work backwards.

Since you want the most expensive meal, your tip will have to be the minimum, 15% of $20. Subtract this amount from the $20. The amount you are left with = cost of meal + tip = x + 10% x = x + 0.1 x = 1.1 x

Solve for x.

Answer 2

Let x = cost of meal

.09x = tax on meal

.15x = tip

x + .09x + .15x ≤ 20

1.24x ≤20

x≤ 16.13