<PRE><B>Question 808234</B>
Main difficulty is writing the equations.
Let number of marbles be R, G and B
G+B=15 (1) (ie non red)
R+B=21 (non green)
R+G=14 (non blue)
add all together:
2G+2B+2R=50
So R+G+B=25 (2)
There are 25 marbles in total
Check:
Substitute (1) in (2): R+15=25
So R=10
Then B=11 and G=4
With a total of 25</PRE>