Katie lunch cost 17 dollars no tax she gave a tip of 18 percent of the cost of lunch what’s the total cost no tax

$20.06

To find how much 18% of the cost is, convert the percentage to a decimal by dividing by 100. Then multiply that decimal to the cost.

18/100 = .18 (percentage as decimal)
17*.18 = $3.06 (18% of the cost)
3.06+17 = $20.06 (total price with tip of 18% and cost)