Answer: D) Samuel earns $20 for each lawn he mows.
Choices A,B,C are not proportional relationships because they are linear equations that do not go through the origin. For instance, choice B's equation is y = 25x+45, showing the y intercept is 45 instead of 0. The direct proportion equation must have a y intercept of 0. Similar situations happen with choice A and C.
Choice D is the answer because the equation here is y = 20x. This line goes through the origin. The constant of proportionality is 20, meaning that each time x goes up by 1, y goes up by 20. In this case, x is the number of lawns mowed and y is the total amount of money made.
