Answer
See below.
Work Step by Step
Let $x$ be the amount loaned out at $8\%$, then $12000-x$ is the amount loaned out at $18\%$, then our equation is: $1.08x+(12000-x)1.18=12000+1000\\1.08x+14160-1.18x=13000\\0.1x=1160\\x=11600$
So $11600$ should be the amount loaned out at $8\%$ and then $400$ is the amount loaned out at $18\%$.