Ch4+br2=ch3br+hbr which type of reaction does this equation represent

this could be a substitution reaction. as you will locate, between the hydrogen's on the propane chain replaced into substituted for a Br from Br2. that's particularly no longer a addition reaction! addition reactions artwork once you have a AlkENE! by using fact that's an AlkANE it would not have a double bond to act as a nucleophile to attack the Br2 (which might act as a electrophile to boot reactions).

Yes you are correct use the scientific method