X-3y, x=3, y=-2
(3)-3(-2)
(3)+(3*2)
3+6=9
Using the vertex of the quadratic function, it is found that:
a) The maximum number of customers in the store is at 12 P.M.
b) 75 customers are in the store at this time.
The number of customers in x hours after 7 AM is given by:

Which is a quadratic equation with coefficients 
Item a:
The maximum value, considering that a < 0, happens at:

Hence:

5 hours after 7 A.M, hence, the maximum number of customers in the store is at 12 P.M.
Item b:
The value is y(5), hence:

75 customers are in the store at this time.
A similar problem is given at brainly.com/question/24713268
Answer:
$1256.85
Step-by-step explanation:
1140 (1.05) = $1197 cost
$1197* 1.05 = 5% profit
<u>Solution-</u>
Let's assume, the rate of interest of $8000 is x%,
then the rate of interest of $17000 is (x+0.3x) =1.3x%
Interest earned by $8000,

Interest earned by $17,000,

According to the question,





∴ Rate of interest of $8000 is 1.96% and rate of interest of $17000 is (1.3×1.96) =2.55%