Explanation:

Correct option 3: 63

Let the number of green balls and blue balls present in the bag be 'g' and 'b' respectively
Also, number of red balls = 17
Total number of balls = (17+ g + b)
Probability of drawing a red ball = 17/(17+ g + b)
Probability of drawing a green ball = g/(17+g+b)
Probability of drawing a blue ball = b/(17+g+b)
Now a/q we have
⇒g/(17+g+b) = 1/7+17/(17+g+b)
(g-17)/(17+g+b) = 1/7
6g-b =136 .....(1)
also,
⇒b/(17+ g + b) = 1/21 + 17/(17+g+b)
⇒(b-17)/(17+ g + b) = 1/21
20b - g  = 374 ....(ii)
using equation (i) and (ii), we get
g = 26, b = 20
.. Required total number of balls in the bag = (26 +20 +17) = 63