Answer:
30 pairs of jeans.
Step-by-step explanation:
Suppose there were x jeans in the case and they cost $y a pair.
Then xy = 900.
After taking out 2 pairs she had x - 2 left and she got y + 10 dollars for each pair.
So (x - 2)(y + 10) = 1120
xy + 10x - 2y -20 = 1120
xy - 2y + 10x = 1140
From the first equation we have y = 900/x so substituting we have:-
900 - 1800/x + 10x = 1140
10x - 1800/x - 240 = 0
Multiply through by x:-
10x^2 - 1800 - 240x = 0
x^2 - 24x - 180 = 0
(x + 6)(x - 30) = 0
so x = 30 pairs of jeans (answer).
Each pair originally cost 900 / 30 = 30 dollars.
CHECKING the answer:-
30 pairs of jeans at $30 = $900
She sold 30-2 = 28 pairs at 30+10 = 40 dollars each.
That is 28*40 = 1120 dollars.
So it checks out.
I hope this helps.
