Julian has an image that measures 12"x18" in size. He knows that he will need background support that is approximately the same size as his image and that his overmat will need an additional three inches on all sides. Based on this, what size overmat will Julian need?

at least 18 X 24
at least 24X32
approximately 16X18
exactly 12X18

Julian will need an overmat that is at least 18"x24" in size.