a store sells the basic model of a phone for $60 and the upgraded model for $200. it costs the store $10 to…

a store sells the basic model of a phone for $60 and the upgraded model for $200. it costs the store $10 to buy each basic model and $50 to buy each upgraded model from the phone company. on tuesday, the store has $1,800 in sales for these two models, and it paid the phone company $400 to buy these phones. how many upgraded models did the store sell on tuesday?\n\n6 upgraded phones\n10 upgraded phones\n15 upgraded phones\n42 upgraded phones

a store sells the basic model of a phone for $60 and the upgraded model for $200. it costs the store $10 to buy each basic model and $50 to buy each upgraded model from the phone company. on tuesday, the store has $1,800 in sales for these two models, and it paid the phone company $400 to buy these phones. how many upgraded models did the store sell on tuesday?\n\n6 upgraded phones\n10 upgraded phones\n15 upgraded phones\n42 upgraded phones

Answer

Explanation:

Step1: Define variables

Let $x$ be the number of basic - model phones and $y$ be the number of upgraded - model phones.

Step2: Set up the sales equation

The selling - price of basic model is $60$ and of upgraded model is $200$, and total sales is $1800$. So, $60x + 200y=1800$, which simplifies to $3x + 10y = 90$ (dividing by 20), and $x=\frac{90 - 10y}{3}$.

Step3: Set up the cost equation

The cost of basic model is $10$ and of upgraded model is $50$, and total cost is $400$. So, $10x+50y = 400$, which simplifies to $x + 5y=40$, and $x=40 - 5y$.

Step4: Equate the two expressions for $x$

$\frac{90 - 10y}{3}=40 - 5y$. Multiply both sides by 3: $90 - 10y=120 - 15y$. Add $15y$ to both sides: $90 - 10y+15y=120 - 15y+15y$, which gives $90 + 5y=120$. Subtract 90 from both sides: $5y=120 - 90$, so $5y = 30$. Divide both sides by 5: $y = 6$.

Answer:

A. 6 upgraded phones