Question

Karen made 40 cakes

Answer 1

1. You have that Karen made 40 cakes and she gives 1/5 to Andrew and 10% to Chris, then you have:

 40 cakes=5/5=1
 1/5 to Andrew⇒40x1/5=8
 10% to Chris=40x0.10=4

 1/5----8 
    x----4 

 x=4(1/5)/8
 x=1/10

 2. The fraction of the 40 cakes that she have left is:

 1-1/5-1/10

 Therefore, the answer is: 7/10