Let N be the number of items sold and p the price.
Since the variation is inverse, then the relation between N and p is:

For N=20000 and p = $9.5, we get the formula:

If p = 8.75, then the number of items sold can be computed using the formula:
You can use the sum and difference identities which for cosine is cos(a+b)= cosacosb-sinasinb
Answer:
3
Step-by-step explanation:
2x + 3 = -x + 12
subtract 3 from both sides
2x = - x + 9
add x to both sides
3x = 9
divide by 3
x = 3
He has $90 in total to spend
He spent (31/45) of this money on ticket
so money spent on ticket =(31/45) *90 =2790/45 =62
Now money left with him is 90-62 =28 $
Now it says that he spent (3/7) of this remaining money at concession stand
so money spent on concession stand =(3/7)*28 =84/7 =12
Now money left with him = 28-12 =16
So money left with him is $16 but hat costs for $18
So Mr. O'Connor didnt have enough moeny to buy the hat