A has 50% of the money B has. B has 80% of the money that C has. If C gives $180 to A, C will have the same as B. How much money do each of them have?

originally:

C = x
B = .8x
A = .4x

after give-away C has x-180

then .8x = x-180
.
.
x = 900

check: C has 900, B has 720, and A has 360
give-away C has 720, B has 720, A has 540

checks out!