3. $\left\{a_{n}\right\}$ is an arithmetic sequence, $a_{1}=1$, with a common difference of $d ;\left\{b_{n}\right\}$ is a geometric sequence, with a common ratio of $q$, the first three terms of the sequence $\left\{a_{n}+b_{n}\right\}$ are $3, 12, 23, d+q=$ $\qquad$ .
3. 9 .

From the conditions, we know that $a_{1}=1, a_{2}=1+d, a_{3}=1+2 d, b_{2}=b_{1} q, b_{3}=b_{1} q^{2}, 1+b_{1}=3,1+d+$ $b_{1} q=12,1+2 d+b_{1} q^{2}=23, b_{1}=2, q=2, d=7$. Therefore, $d+q=9$.