15 campers went rowing in the morning. Some more campers went rowing in the afternoon. If a total of 32 campers went rowing that day how many campers went rowing in the afternoon?
Let's denote the number of campers who went rowing in the morning by x. Then the number of campers who went rowing in the afternoon is 32-x. 

Therefore the answer (numeric) is: 

32-x = 32-15 = 17