Explanation

Given: a/b = 3/5 ... (1)

When 2 is added to both numbers, the ratio becomes 2/3, so we can write:

(a+2)/(b+2) = 2/3 ... (2)

Cross-multiplying (2), we get:

3(a+2) = 2(b+2)

Expanding and simplifying, we get:

3a + 6 = 2b + 4

Subtracting 6 from both sides gives:

3a = 2b - 2

Now, substituting (1) in the above equation, we get:

3(3/5)b = 2b - 2

Multiplying both sides by 5, we get:

9b = 10b - 10

Subtracting 10b from both sides gives:

-b = -10

Dividing both sides by -1, we get:

b = 10

So, the correct answer is: 10