Solution:
We will let x = be the whole class.
From the situation stated above, we can deduce the following facts:
(2/3)x = students wearing BLUE JEANS.
(2/6){(2/3)x)} = students wearing BLUE JEANS and RED SHIRT.
THEREFORE: (4/18)x = students wearing BLUE JEANS and RED SHIRT.
Reducing fraction to lowest term: we will have
(2/9)x = students wearing BLUE JEANS and RED SHIRT
Thus 2/9 is the fraction of the class "x" wearing BLUE JEANS and RED SHIRT.