word problem: choosing between 2 plans at discount warehs

[birdie77]

you are choosing between two plans at a discount warhouse. Plan A offers an annual membership fee of $100 and you pay 80%of the manufacturer's recommened lise price. Plan B offers an annsual membership fee of $40 and you pay 90% of the manufacturer's recommended list price. How many dollars of merchandise would you have to purchase in a year to pay the same amount under both plans? What will be the cost for each plan?

 

[skeeter]

let D = total dollars spent in purchasing merchandise

Plan A cost = 100 + (.80)D

Plan B cost = 40 + (.90)D

you want to find D such that the two costs are equal ... what's next?