Monica earned $18.50, $23.00, and $15.00 mowing lawns for 3 consecutive weeks she wanted to earn an average of at least $18 per week. what is the minimum she should earn during the 4th week to meet her goal?

Add the four weeks of earnings, divide them by four and this equals the average of $18 per week.

x= fourth week earnings

18= ($18.50 + $23 + $15 + x)/4
multiply both sides by 4
72= 56.50 + x
subtract both sides by 56.50
15.50= x

ANSWER: She must earn $15.50 the fourth week to average $18 per week.

Hope i can you!