Question

a and b have equal amount of liquid. 120ml is poured from a to b. container b now contains 4 times as much liquid as a.how much is in a

Answer 1

let the equal amount be x ml each
after the pouring event:
a has x-120
b has x+120

b = 4a
x + 120 = 4(x-120)
x+120 = 4x - 480

etc , so easy from here on

Answer 2

480-120=360
360 divided by 4 = 90