Question 770021
Bob's weight is double that of joe and their combined weight is 225 lbs. 
Let joe weight "x" lbs.
Then Bob weighs "2x" lbs.
-----------------------
Equation
x + 2x = 225
3x = 225
x = 75 lbs (Joe's weight)
--------------------------------
Bob weighs 2x = 150 lbs 
Cheers,
Stan H.
====================