math
posted by Anonymous .
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?

X = the total # of tshirts.
3x/7 = the # of red tshirts.
x/3 = the # of blue tshirts.
(3x/720)=The # of blue tshirts,also.
x/3 = 3x/7  20,
x/3  3x/7 = 20,
Multiply both sides by 21:
7x  9x = 420,
2x = 420,
X = 210.
3x/7 = 3*210 / 7 = 90 Red tshirts.
x/3 = 210 / 3 = 70 Blue tshirts.
Y = 210  90  70 = 50 Yellow tshirts.