Respuesta :

m(3.4) - n(-8.7)

First, substitute in your numbers for m and n. / Your problem should look like: 
Second, subtract 3.4 - -8.7. / Your problem should look like: 12.1

Answer: 12.1 (D)
3.4 - (-8.7) = 12.1

I hope this helps. (: