12/10 + 9/10 = 21/10
21/10 simplified is 2 1/10
-0.24 should be the answer. idk i might be wrong. im not to great at math just i just used a calculator
Answer
Subtract
from 
then;

Remove the bracket we have;

Like terms are those terms which have same variable to the same power.
Combine like terms;

Therefore, Subtracting
from
we get 