w campers went rowing in the morning. Some more campers went rowing in the afternoon. If a total of x campers went rowing that day How many campers went rowing in the afternoon?
First, we know that some campers went rowing in the morning. This means that not all campers went rowing in the morning, because if all campers went rowing in the morning, then there would be no campers left to go rowing in the afternoon! So, we can write:

Some campers went rowing in the morning. 

This means that the number of campers who went rowing in the morning is less than the total number of campers, or:

The number of campers who went rowing in the morning < the total number of campers

We also know that some more campers went rowing in the afternoon. This means that the number of campers who went rowing in the afternoon is greater than the number of campers who went rowing in the morning, or:

The number of campers who went rowing in the afternoon > the number of campers who went rowing in the morning

We also know that the total number of campers who went rowing that day is x. This means that the number of campers who went rowing in the morning plus the number of campers who went rowing in the afternoon is equal