Word problems often appear on important tests. It's important to stay calm and take your time and read the problem carefully. Word problems aren't usually all that difficult as long as you take a deep breath and read them carefully (which is sometimes difficult when you feel pressured by a test).
There were 23 flies in Jill's house. She tracked down and swatted 13 of them. How many flies are left?
23 - 13 = 10