A cell phone store sells the basic model of a phone for $30 and the upgraded model for $100 when a customer signs a two-year agr
eement. On Tuesday, the store has $900 in sales. The store pays $5 for each basic model and $25 for each upgraded model. If the cost of the cell phones sold on Tuesday is $200, how many upgraded models were sold?
<span>You need to set up 2 equations for this, a system to be exact
let x represent the cheaper phone and y represent the upgraded phone
for store costs you will have
5x+25y=200
for selling prices you will have 30x+100y=900
set these two equations together
5x+25y=200
30x+100y=900
multiply the first one by -4 and add them
-20x-100y=-800
30x+100y=900
10x=100
x=10
10 cheaper phones, plug into any equation again
5(10)+25(y)=200
y=6<<<6 upgraded phones</span>
