Let,
the no. of adults be "x"
then, the no. of childern = total people - total adults
= (30 - x)
Now,
According to the quesiton,
2 (30 - x) + 5x = 87
60 - 2x + 5x = 87
60 + 3x = 87
3x = 87 - 60
3x = 27
x = 27 / 3
x = 9
So, there were 9 adults in the group
The formula for this is: (sale price) / (1 - percentage)
Percentage have to be in decimal form, so divide percentage by 100 to get the decimal form.
220/(1-.20) = $275
The original price was $275.
Base of the exponential equation should be (-1).
And finally the product or result should also be a negative number.
Let us take a variable for n natural numbers.
(Note: All positive whole numbers are called natural numbers that is 1,2,3,4,5,....).
In order to get the expression, we need to find the expession for odd natural numbers.
We know,
The expession for odd natural numbers is given by = 2n-1.
Where n= 1,2,3,4,5...
If we have an odd exponent of a negative number, it always gives a negative number.
We got, base = -1 ( a negative number) and
exponent = (2n-1) ........... expression for odd number.
Therefore, we could write final exponential expression that would give a negative for all natural numbers.

The answer is 173 ft²
The area of the patio (A) is half of the area of the circle (A1) with a diameter of 21 ft:
A = A1/2
The area of the circle with radius r is:
A1 = π * r²
π = 3.14
We do not have the radius, but we know that it is a half of the diameter:
r = 21 ft / 2 = 10.5 ft
A1 = 3.14 * (10.5)² = 346.18 ft²
So, the area of the patio is:
A = A1/2
A = 346.18 ft² / 2
A = 173.09 ft² ≈ 173 ft²