Olivier Giroud gave Arsene Wenger’s men the lead on the stroke of half-time with a fine finish, before Ramsey made the points secure when he fired home in the 81st minute after intricate build-up play.
Substitute Mathieu Flamini added gloss to the scoreline when he tapped in from close range following Santi Cazorla’s low pass across goal.
Mertesacker was clearly delighted at helping the north London side move to within a point of second-placed Manchester City.
The German defender uploaded the photo above of himself and Ramsey onto his Twitter account after the game and wrote: “Happy for the team and especially for @aaronramsey … Thanks for your support gooners. #AFCvsWHU”
Arsenal travel to Monaco in the Champions League on Tuesday night as they aim to overturn a 3-1 first-leg deficit from the first leg of their last-16 tie.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news