Jen and Heather went to lunch. When the bill came, Jen discovered she had only $6. Luckily, Heather had enough money to pay the other part, or 3/5 of the bill. How much did Heather pay and how much was the total bill? Please explain how you got these answers.

2/5x=6

That's the total bill.
Heather paid 3/5 of that.