Rachel had to complete w pages of math homework, x pages of reading homework and y more pages of biology homework. How many pages of math and biology homework did she have to complete?
First, we need to find out how many pages of math and biology homework Rachel had to complete. We know that she had to complete w pages of math homework and y more pages of biology homework. This means that she had to complete w + y pages of math and biology homework. 

Now, we need to find out how many pages of reading homework she had to complete. We know that she had to complete x pages of reading homework. 

This means that the answer (symbolic expression) is: 

w + y + x