What affects does adding a constant have to an exponential function? (someone told me that it makes the graph shift left or right, and someone else said that it shifts the graph up and down)

As a self-employed seamstress, you know that it takes 7 yards of material to make 3 jackets. you bought 15 yards of material to make 7 jackets. did you buy enough material? if not, how much were you over or under?