There are 17 members in the scout troop all of the members went on a trip to a state park there were also 4 adults on the trip what was the total cost c if the admission for each person was 3$

There were a total of 17 + 4 = <<17+4=21>>21 people on the trip.

The total cost of admission for each person is 21 x $3 = $<<21*3=63>>63. Answer: \boxed{63}.