Hi Channy149.
Whether the two procedures that you are inquiring about (brachioplasty, breast augmentation/lift) can be performed simultaneously will largely depend on your surgeon's preference and comfort level. Depending on your clinical state, what needs to be done, and the amount of time that is required, your surgeon may choose to split the two procedures over two stages. There are pros and cons to performing multiple procedures on the one occasion. Obviously doing both together will subject you to just one anaesthetic and hospital stay. However, the longer the procedure, the greater degree of potential complication (general anaesthesia, electrolyte imbalance, infection etc etc), and the more significant the recovery. Your plastic surgeon will be the best person to decide if it's best to do it on two separate occasions or simultaneously. 

All the very best.
Dr Ray GohValley Plastic Surgery