a) Joelle has y = 18 + 4x, where x represents the number of weeks.
Explanation: Joelle currently has 18 rocks in her collection, and she gains 4 rocks each week. We represent the number of weeks as x. Therefore, the equation for Joelle's collection would be y = 18 + 4x, where y represents the number of rocks in her collection.
b) Lewis has y = 30 + 3x, where x represents the number of weeks.
Explanation: Lewis currently has 30 rocks in his collection, and he gains 3 rocks each week. Similar to Joelle, we represent the number of weeks as x. Therefore, the equation for Lewis's collection would be y = 30 + 3x, where y represents the number of rocks in his collection.
c) To determine the number of weeks for Joelle and Lewis to have the same number of rocks, we set their equations equal to each other:
18 + 4x = 30 + 3x
Explanation: We are trying to find the point at which both Joelle and Lewis have the same number of rocks in their collections. By setting their equations equal to each other, we can find the value of x (number of weeks) that satisfies this condition.
d) To determine the number of rocks Joelle and Lewis will have when their collections are equal, we substitute the value of x into either equation:
Using 18 + 4x:
Rocks in Joelle's collection = 18 + 4x
Rocks in Lewis's collection = 18 + 4x
Explanation: Since x represents the number of weeks, we substitute the value of x into either Joelle's or Lewis's equation to find the number of rocks in their collections when they have the same quantity. Both individuals will have the same number of rocks in their collections.