If A received 30 from B, A would have twice B.
If B received 50 from A, B would have thrice A.
How much do A and B have?
solving:
A+30=2*(B-30) (i)
3*(A-50)=B+50 (ii)
Mult. (ii) by 2 and subtract (i):
5*A=490
A=98
B=1/2 * (98+30) + 30 =64+30=94
answ: (A,B)=(98,94)