There were 2/3 as many rubber bands in Box A as in Box B. After 156 rubber bands were transferred from Box B to Box A, there were twice as many rubber bands in Box A as in Box B. How many rubber bands were there in Box B at first?

Answer 1

at the start:
box B --- x rubber bands
box A = (2/3)x bands

after the move:
boxB = x - 156
boxA = (2/3)x + 156

result:
(2/3)x + 156 = 2(x - 156)
2x/3 + 156 = 2x - 312
2x/3 - 2x = -468
-4x/3 = -468
x = 351

Box B had 351
Box A had (2/3)(351) = 234

check:
at the start:
boxB --- 351
boxA ---- 234
after the move:
boxb = 351-156 = 195
boxA = 234+156 = 390 , which is twice 195.
My answer is correct