check the air in the tires, if all ok check the brake caliper in the right wheel it mite be locking up or not working properly, mite be need lubed or replaced

When a car pulls to one side while applying the brakes, this usually means that the opposite side is not working, or not working as well as the side that it's pulling to.This means that if the car is pulling to the right then the left side is not working properly. The car "pulls" to the right because when appling the brakes the side that is working will stop the wheel,which in your case is the right wheel, while the left wheel still turns. The "pulling" is actually caused by the car "pivoting" on the right front wheel.