Shakira bought a case of jeans for $900. she kept two for herself and sold the rest for $1,120 ,making a profit of $10 on each pair of jeans. how many jeans were in a case?

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 -

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.