You have a photo that measures 1 in. wide by 3 in. tall. If you want to enlarge the photo so that the height is 18 in., what will the width of the photo be?
The height of the photo goes from 3 in. to 18 in. To get from 3 to 18 we multiply by 6. So, we must multiply the width by 6 to make sure that our photo is up to scale after the enlargement. Well 6*1= 6, which will be your final width.