Jeff had $20. he spent 1/8 of his money on lunch and 2/5 of his money at the movies. how much money does jeff have left?

The total amount of money that Jeff has is $20
total fraction of his expenses on lunch and movies is:
(2/5+1/8)
=21/40
the remaining fraction is:
1-21/40
=19/40
thus the amount of cash that Jeff was left with will be:
19/40×20
=$ 9.5