Divide
Split, go halves in/with, go Dutch, divide, and go fifty-fifty in.
Apportion
Apportion, divide up, ration out, distribute, hand out, deal out, parcel out, carve up, portion out, allocate, give out, dispense, dish out, dole out, measure out, and divvy up.
Partake in
Participate in, play a part in, be involved in, have a hand in, partake in, have a percentage of, take part in, have a role in, contribute to, have something to do with, have a share in, and have a stake in.