May i know how u get 1840? Next 3 units should be 92 x 3 = 276...when u mention 20 units = 1840 divide by 20 units in order to find 1 unit.

I obtained a different answer of $270 at the end as explained in the question’s comments section.

In summary, I got these:

Before

Box A: 400 pieces 50c, 180 pieces $1
Box B: 160 pieces 50c, 1100 pieces $1

Transfer made is 380 pieces 50c, 160 pieces $1

After

Box A: 20 pieces 50c, 20 pieces $1 (so percentage of 50c is 50%)
Box B: 540 pieces 50c, 1260 pieces $1 (so percentage of 50c is 30%)

For a total value of $270 worth of 50c coins in Box B.

This is just my line of thought and may not represent a correct solution or working.

Rachael, Box B started out with

160 pieces of 50c coins

at first, so there could not have been

92 pieces of 50c coins

in Box B at the end, considering that coins are being transferred from Box A to Box B but no coins are being transferred from Box B to Box A.

Edit: Had not seen your updated comments of 276 coins in time.

One flaw I spotted in Rachael’s working is that the “1/2” and “3/10” cannot be actually added together, since we are not actually dealing with the same number of coins in both boxes.

The fractions 1/2 and 3/10 in “1/2 of 100 coins and 3/10 of 100 coins” can be added

but

the fractions 1/2 and 3/10 in “1/2 of 100 coins and 3/10 of 500 coins” cannot be added.

I decided to give Rachael an upvote for the effort that she has put in, although there is a slight inaccuracy in the concept of the working.

That's cool. Mandy remember to thank your tutors Rachael and Eric too! Happy learning. :)