For this case we assume that the initial amount of money is $20.
So:
[tex]\frac {1} {5} (20) = 4[/tex]
[tex]\frac {3} {8} (20) = 7.5[/tex]
[tex]\frac {2} {7} (20) = 5.71[/tex]
Adding we have:
[tex]4 + 7.5 + 5.71 = 17.21[/tex]
Ken has:
[tex]20-17.21 = 2.79[/tex]
Answer:
Ken can spend what he planned and he has $2.79 left.