I'm greater then 15 and less then 40. if you double me i become a number that ends in 0. and a 1/5 of me is equal to five. who am I?

Answer 1

25

Answer 2

This might help you see the process in reaching the answer.

The last clue is the best. Let x = the number.

1/5x = 5

Multiply both sides by 5.

x = 25

Does that fit the other data?