Question

Brad spent 20 percent of his money to buy a car costing £6800 how much did he have

Answer 1

There are few ways but i prefere this way:

100/20=5
6800*5=?
6000*5=30000
800*5= 4000
+-----------
= 34000

=£34000

Answer 2

He had 34000 euros total.  Divide 6800 by 0.2 (AKA 20%)