The total number of sheep the farmer has is 113 sheep. Since 47 of them are males and you are solving for the number of female sheep, you can subtract 47 sheep from 113 sheep.
113 - 47 = 66
We have figured out that there are 113 total sheep, 47 male sheep, and 66 female sheep. The question is asking for how many more female sheep are there than male sheep, so subtract the number of male sheep from the number of female sheep.
female sheep - male sheep = answer
66 - 47 = 19
There are 19 more female sheep than there are male sheep.