I am stuck can someone help me

19.2 - 21.1
----------
3.18
\/25

I'm assuming your problem is this:

(19.2 - 21.1)/(3.18/√25)

Calculating:
(-1.9)/(3.18/5) =
(-1.9)/(0.636) =
-2.99 (rounded to two decimal places)

I hope this helps and is what you were asking.