In the first 2 hours after Meadow's self-service laundry opens, m larg

official solution

During the two-hour period each large washer does four loads (the number of 30-minute periods in two hours is four) and each small washer does six loads (the number of 20-minute periods in two hours is six). Therefore, the total number of loads done during the two-hour period by m large washers and n small washers is 4m + 6n.

If m = 1 and n = 3, then n = 3m and the total number of loads of laundry done in the two-hour period is 4(1) + 6(3) = 22. However, if m = 2 and n = 6, then n = 3m and the total number of loads of laundry done in the two-hour period is 4(2) + 6(6) = 44; NOT sufficient.
Since 2m + 3n = 55, it follows that 4m + 6n = 110. Therefore, by the remarks above, the total number of loads done during the two-hour period is 110; SUFFICIENT.