The best thing to find out how much he has already saved.
As you're looking for 60%, the best thing to do is to find 10% and then multiply accordingly.
To find ten percent, divide 120 by 10.
therefore, 10% is $12.
As you're looking for 60%, you need to multiply this by 6.
12*6= 72.
So far, Ashton has saved $72, and you're looking for what is left, so you need to subtract this from 120.
120-72= 48
therefore, Ashton needs to save $48 more to buy the bike.
Hope this helps :)
