Probability Question -- Choosing red and white coins from two tables

[nothing909]

Homework Statement

table 1 has 3 red and 5 white coins. table 2 has 4 red and 2 white coins. a coin is chosen at random without knowing its color from table 1 and placed onto table 2. then as coin is taken from the second table. what is the probability that the coin chosen from the second table is white?

Homework Equations

The Attempt at a Solution

The answer is 21/56, but, I'm unsure how to work this out.

What I have tried is:

there is a 5/8 probability of a white coin being taken from table 1 and placed onto table 2.

then, from table 2, I assumed that the white coin from table 1 has been added, so, now there is 3 white coins on table 2.

I then did 3x(5/8) / 7, which gives me 15/56.

 

[willem2]

there is a 5/8 probability of a white coin being taken from table 1 and placed onto table 2.
then, from table 2, I assumed that the white coin from table 1 has been added, so, now there is 3 white coins on table 2.
I then did 3x(5/8) / 7, which gives me 15/56.

This is ok. Now there is also a probability that a red coin was taken from table 1 and onto table 2.