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?

6 upgraded phones

10 upgraded phones

15 upgraded phones

42 upgraded phones

Simple Answer - 6 upgraded phones

6 upgraded phones

Step-by-step explanation:

Let the number of basic model phones sold on Tuesday be "x" and the number of upgraded model phones be "y".

Sale price of each basic model phones is $60, so the sale price of x basic model phones will be $ 60x

Sale price of each upgraded model phones is $200, so the Sale price of y basic model phones will be $ 200y

On Tuesday, the store has $ 1800 in sales. This was the sales from x basic model and y upgraded model phones. So, based on the above data, we can set up the equation as:

60x + 200y = 1800 Equation 1

Cost of each basic model phones is $10 so the cost of x basic model phones will be $ 10x

Cost of each upgraded model phones is $50, so the cost of y basic model phones will be $ 50y

The store paid $400 to buy these x basic model and y upgraded phones. So, based on the above data, we can set up another equation as:

10x + 50y = 400 Equation 2

Multiplying the Equation 2 by 6 and subtracting it from Equation 1 we get:

60x + 200y - 6 (10x + 50y) = 1800 - 6 (400)

60x + 200y - 60x - 300y = 1800 - 2400

- 100y = - 600

y = 6

Since, y represents the number of upgraded phones, we can conclude that the store sold 6 upgraded phones on Tuesday.