When would it be more useful to represent a proportional relationship with a graph rather then an equation

If kn = 9 cm, mn = 21 cm, rs = 42 cm, and ps = 18 cm, what is the scale factor of figure klmn to figure pqrs?

Astandard american eskimo dog has a mean weight of 30 pounds with a standard deviation of 2 pounds. assuming the weights of standard eskimo dogs are normally distributed, what range of weights would 99.7% of the dogs have? approximately 26–34 pounds approximately 24–36 pounds approximately 28–32 pounds approximately 29–31 pounds

At a sale this week, a desk is being sold for $213. this is a 29% discount from the original price. what is the original price?