⓵ In order to find your answer, you need to do a cross product. If it helps, you can say it in a sentence before actually writing the numbers down :
↠ When 2 serves land in, there are always 5 serves that also landed out in the process. So when 28 serves land in, how many serves also landed out in the process (×)?
⓶ Once you’ve actually understood what you are looking for, you can go ahead and do your cross product :
2 in → 5 out
28 in → × out
(5 x 28) ÷ 2 = ×
↓
(140) ÷ 2 = ×
↓
70 = ×
★ So your answer is :
If Fred hit 28 serves in, 70 serves landed out.
I hope this helped, if there’s anything just let me know! ☻