i would like to ask....

1/6 of the black balls are taken away,
therefore,
there are (1 - 1/6) = 5/6 ot the black balls remaining in the bag.

1/2 of the white balls are taken away,
therefore,
there are (1 - 1/2) = 1/2 of the white balls remaining in the bag.

Therefore,
the required equation is,

5/6x + 1/2y = 57

Then, we mutiply 6 both sides of the equation in order to make the coefficients of x and y into integers.

The equation becomes,

5x + 3y = 342