A sandbox is 7/9 of the way full of sand. You scoop out 3/7 of the sand which is currently in the box. What fraction of sand (in relation to the entire box) is left in the sandbox?
x = full box
7/9 x - 3/7 (7/9 x )
7/9 x - 21/63 x
(49/63 - 21/63 ) x
28/63 of x is left ( 4/9 ths is left)