Answer: Sali gets 6 cakes. Jane gets 3 cakes. Simon in the end keeps 21 cakes.
Step-by-step explanation: 1/5 of 30 is 6 so if Sali gets 1/5 then Sali should get 6 cakes. 10% of 30 is 3 so if Jane gets 10% then she should get 3 cakes. Sali and Jane together get 9 cakes so Simon has 21 cakes left.