So here we just want to divide 7/8 by 1/5, to find how many 1/5, or hours, fit into 7/8.
To divide, you just want to reverse the second fraction and then multiply.
1/5 reversed is 5/1.
7/8 * 5/1 = 35/8
35/8 converted to a mixed number would be 4 3/8.
So it would take 4 3/8 hours for the entire pot of water to evaporate.