To celebrate his 30thBirthday, Luigi paid for a round of drinks with a £50 note. If he had spent £10 more, he would have received a third as much change. How much did he spend in total?
Spent x on first round, got 50-x change.
If spent (x+10), would have gotten (50-x)/3 change. His change would be 50-(x+10) = 40-x.
So 40-x = (50-x)/3
Can you solve for x?