Answer:
each person can get 3/12 if you split the 3.4 twice.
Explanation:
make a circle
split one line down the middle and the other horizontal.
color is one of the corners. you will not use it. this is the part of the cake they already ate.
now you have three remaining parts.
split each one of the remaining heart down the middle.
now you have six remaining slices.
6 is not divisible by 4.
split the sixths down the middle one more time.
now you should have 12.
12 is divisable by 4.
give each person 3 out of 12 slices of cake.
it is just enough to feed all 4 people.