Answer
$-5260$
Work Step by Step
The nth term of an arithmetic sequence can be obtained by the formula $a_n=a_1+(n-1)d$ where $a_1$ is the first term and $d$ is the common difference.
The nth term of a geometric sequence can be obtained by $a_n=a_1\cdot r^{n-1}$ where $a_1$ is the first term and $r$ is the common ratio.
Hence here: $a_{11}=-5(-2)^{11-1}=-5(-1024)=-5120$
$b_{11}=10+(11-1)(-15)=10+(-150)=-140$
Then $a_{11}+b_{11}=-5120=-140=-5260$
