Answer:
x=47, y=68
Step-by-step explanation:
Add the two equations. Then we get
-y=-68
y=68
Substituting the value of y in the first equation,
8x-6(68)=-32
8x-408=-32
8x=376
x=47
Answer:
The number of persons using the elevator at any hour is never going to be less that 15.
Step-by-step explanation:
To solves this you have to suppose that there are at least 15 persons on the elevator, and the equation is converted into an inequation:
Now you transform the inequation back to an equation to solve it:

You need to know if there is any negative solution for the equation, to do this you can use the discriminant for a quadratic equation:

In this case, you have a=1, b=-10, c=25

Since the discriminant is 0 and a<0 the equation always is going to be positive. Therefore, the number of persons using the elevator at any hour is never going to be less than 15.
Answer:
36x² - 9y²
Step-by-step explanation:
We see that the given expression (6x + 3y)(6x - 3y) looks just like the expression (a + b)(a - b). When multiplied out, this is a difference of squares identity that I highly recommend you memorise:
(a + b)(a - b) = a² - b²
Here, a = 6x and b = 3y, so plug these in:
(6x + 3y)(6x - 3y) = (6x)² - (3y)² = 36x² - 9y²