The total cost y, in dollars, of buying the materials and renting the tools for x days from Store A and Store B is found by substituting the respective values for these stores from the table into the given equation,y=M+(W+K)x, as shown below.
Store A:y=750+(15+65)x=750+80x StoreB:y=600+(25+80)x=600+105x
Thus, the number of days, x, for which the total cost of buying the materials and renting the tools from Store B is less than or equal to the total cost of buying the materials and renting the tools from Store A can be found by solving the inequality 600+105x≤750+70x. Subtracting 80x and 600 from each side of 600+105x≤750+70x and combining like terms yields 25x≤150.Dividing each side of 25x≤150 by 25 yields x≤6.Choice B is incorrect. The inequality x ≥ 6 is the number of days for which the total cost of buying the materials and renting the tools from Store B is greater than or equal to the total cost of buying the materials and renting the tools from Store A. Choices C and D are incorrect and may be the result of an error in setting up or simplifying the inequality.