To determine the number of lawns he needs to mow to earn the desired money, Eli could perform a simple addition problem, adding $21 per lawn until he reached his goal number. This equation would be: 21 + 21 = 42 + 21 = 63 + 21 = 84 + 21 = 105 + 21 = 126 + 21 = 147 + 21 = 168 + 21 = 189 + 21 = 210 + 21 = 231 + 21 = 252. However, a better way would be to divide the desired amount by the cost per lawn and round to the nearest whole number. That equation is 235 / 21 = 12 lawns.
