A farm has a total of 50 cows, horses, and goats. The number of goats is 5 more than the number of cows, and there are 10 fewer goats than horses. How many horses are on the farm?

It's a wrong question.
Answer cannot be obtained in whole numbers, which is not possible.

Here is how to set it up; and you might discover that the question is wrong.
Let x = the number of cows.
Then, x + 5 = number of goats.
Then, (x + 5) - 10 = the number of horses.
So, if the total is 50, then:
x + (x + 5) + (x + 5) - 10 = 50.
If you solve for x, which is the number of cows, then you get a fraction of a cow: which isn't possible.
So the total of 50 must be wrong.