Hello;
It has been ages since I've done this kind of problem but here it goes ...
dans fish = 4x
pauls fish = 1x
joes fish = 2x (1/2 of dans fish).
All three fish weigh a total of 21 pounds.
So lets write it this way:
4x + 1x + 2x = 21
or
4 +1 +2 * x =21
or
7 * x =21
or
x = 7/21
so
x =3
-------------------------
Dan's fish = 12 pounds
Paul's fish = 3 pounds
Jose's fish = 6 pounds
There is probably a different way of writing the problem but that is the way I would solve it.
Best of luck,
Bill