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?\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?\n6 upgraded phones\n10 upgraded phones\n15 upgraded phones\n42 upgraded phones

Answer

Answer:

A. 6 upgraded phones

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 equations based on sales and cost

The sales equation is $60x + 200y=1800$, which simplifies to $3x + 10y = 90$ (dividing by 20). The cost equation is $10x+50y = 400$, which simplifies to $x + 5y=40$ (dividing by 10), and then $x=40 - 5y$.

Step3: Substitute $x$ into the sales - simplified equation

Substitute $x = 40-5y$ into $3x + 10y=90$. We get $3(40 - 5y)+10y=90$.

Step4: Expand and solve for $y$

Expand: $120-15y + 10y=90$. Combine like - terms: $120-5y=90$. Subtract 120 from both sides: $-5y=90 - 120=-30$. Divide both sides by $-5$: $y = 6$.