Check the picture below.
now, since we know what "f" is, let us use the CNT triangle with the small COR one.

Weight of man and paint = 160 + 5 = 165 total pounds.
Gravitational force is independent of the path taken so we can ignore the radius of the silo.
Work done = total weight x height
The problem says he climbs to the top so overall height is 90 feet
Work = 165 lbs x 90 ft = 14,850 ft-lbs
I would recommend going to school
Or get a tutor
Or ask your parents