Question 2569
Let the number of A stock be a
and the number of B stock be b

Now one share of A stock is worth 31/2 shares of B stock
=> a = 3 1/2 b
=> a = 7/2b

Now
a + b = 9000
=> 7/2b + b = 9000
=> 9/2b = 9000
=> b = 2000
=> a = 7/2*2000 = 7000

So in stock A $7000 is invested and in stock B $2000 is invested