Posted by Katherine on Monday, March 7, 2011 at 4:47pm.
In a department store, there were a certain number of red Tshirts, blue Tshirts, and yellow Tshirts. 3/7 of the Tshirts were red, 1/3 of them were blue and the rest were yellow. If there were 20 more red Tshirts than blue Tshirts, how many yellow Tshirts were there?

math !!!! :O  MathMate, Monday, March 7, 2011 at 9:20pm
Let the number of Tshirts be
R, B, Y
R=(3/7)(R+B+Y)...(1)
B=(1/3)(R+B+Y)...(2)
Y=(13/71/3)(R+B+Y)...(3)
=(5/21)(R+B+Y)
RB=20 ...(4)
Start with the last equation (4):
(3/71/3)(R+B+Y)=20
2/21(R+B+Y)=20
Solve for (R+B+Y), I get 210.
Substitute (R+B+Y)=210 into (1), (2) and (3) to get the number of tshirts of each colour.