For Erin, the graph shows 10 pounds of sugar are used for every 30 cups of tea.
For Lucia, we can let x=3 and we find 3 pounds of sugar are used for 10·3 = 30 cups of tea.
For the same number of cups of tea (30), Erin uses 10 pounds of sugar and Lucia uses 3 pounds of sugar.
Erin uses sugar at a higher rate.
