Voted Best Answer
Aug 20, 2015 - 07:49 PM
I believe the use of "a" (to) before "comer" (to eat) is because you are saying "I am going to go to the office and "to" eat with Sandra", "Voy a ir a la oficina con a comer con Sandra". The sentence wouldn't sound correct in Spanish if it it read as, "Voy a ir a la oficina y comer con Sandra."