If you would like to know how much weed killer will Alan need for two fields, you can calculate this using the following steps:
two fields: 22 1/2 acres + 38 1/4 acres = 45/2 + 153/4 = 90/4 + 153/4 = 243/4 = 60.75 acres
4/5 of a quart = 0.8 quart ... 1 acre of land
x quarts = ? ... 60.75 acres of land
0.8 * 60.75 = 1 * x
x = 0.8 * 60.75
x = 48.6 quarts
The correct result would be 48.6 quarts of weed killer.