To find the sum of -12.34 and -8.5, you simply add the two numbers together:
\[ -12.34 + (-8.5) = -12.34 - 8.5 \]
To perform the addition more easily, you can convert -8.5 into a decimal with two decimal places:
\[ -8.5 = -8.50 \]
Now add the two numbers:
\[ -12.34 - 8.50 = -20.84 \]
So, the sum of -12.34 and -8.5 is \(-20.84\).