Algebra question

Question

Two containers A and B begin with equal volumes of liquid. 120 ml is then poured from A to B. Container B now contains 4 times as much liquid as A. Find the volume of liquid left in container A.

Answer 1

B + 120 = 4(A - 120)

B + 120 = 4A - 480

Originally, A = B

Substitute:

B + 120 = 4B - 480

3B = 600

B = 200

A = 200

B + 120 = 320

A - 120 = 80