Add.

To add the two expressions \((3y + 2)\) and \((9y + 3)\), you combine like terms.

1. Combine the \(y\) terms: \(3y + 9y = 12y\)

2. Combine the constant terms: \(2 + 3 = 5\)

Putting it all together, you get: \[ (3y + 2) + (9y + 3) = 12y + 5 \]

So, the final result is: \[ 12y + 5 \]