The point $(a, b)$ lies on the line with the equation $3x + 2y = 12.$ When $a = 4$, what is the value of $b$?
To find the value of $b$, I need to plug in $a = 4$ into the equation of the line and solve for $b$. So I get $3 \times 4 + 2b = 12$, which simplifies to $12 + 2b = 12$. Subtracting $12$ from both sides, I get $2b = 0$. Dividing by $2$, I get $b = 0$. Therefore, the point $(4, 0)$ lies on the line $3x + 2y = 12$. 