Respuesta :
Answer:
The answer is (-41/36)
Step-by-step explanation:
The LCD of 9 and 12 is 36
9 x 4 = 36
12 x 3 = 36
(-20/36) + (-21/36) = (-41/36)
Leave the simplest form to how your teacher wants it, either as a mixed number or just leave it like that.