80% of the astronomy club members own a telescope. If 20 students own a telescope, how many students are in the astronomy club in all? help

Aplane flies around trip to philadelphia it flies to philadelphia at 220 miles per hour and back home with a tailwind at 280 miles per hour if the total trip takes 6.5 hours how many miles does the plane fly round trip

What is the result of adding the system of equations? 2x+y=4 3x-y=6

In a two-digit number the units' digit is 7 more than the tens' digit. the number with digits reversed is three times as large as the sum of the original number and the two digits. find the number.