Answer:
To find the value of this expression you need to add and subtract from left to right
74.9+5.23-81.4-16 (add the first two, first)
80.13-81.4-16 (74.9+5.23=80.13) (next subtract the next two)
-1.27-16 (80.13-81.4=-1.27) (Last subtract the last two)
-17.27 (-1.27-16=-17.27)
-17.27
Hope this helps ;)