Answer:
D.

Explanation:
We have been given that a bag contains x blue chips and y red chips. The probability of selecting a red chip at random is 3/7. We are asked to find the
.



Since we are told that probability of selecting a red chip at random is 3/7, so red balls are 3 and total balls are 7:

Since total balls are 7, so we will get:

Upon substituting
in expression
, we will get:

Therefore, the value of
is
and option D is the correct choice.