Answer:
10.4
Step-by-step explanation:
Let the number be x
Sum of x and -3.2 : x + (-3.2) = x - 3.2
1/4 times the sum of a number and −3.2 = (1/4) * (x - 3.2)

x = 10.4
First let's find out how many cups serve one person.
3 ÷ 5 = 1.6
1.6 of a cup serves one person.
1.6 × 13 = 20.8
It takes 20.8 (21 rounded) to serve 13 people.
Answer:
y = -
x + 2
Step-by-step explanation:
The equation of a line in slope- intercept form is
y = mx + c ( m is the slope and c the y- intercept )
Calculate m using the slope formula
m = (y₂ - y₁ ) / (x₂ - x₁ )
with (x₁, y₁ ) = (0, 2) and (x₂, y₂ ) = (4, 0) ← 2 points on the line
m =
=
= - 
The line crosses the y- axis at (0, 2) ⇒ c = 2
y = -
x + 2 ← equation of line
Change the function into vertex form:
f(x)=x²-10x+16
make a square by (adding half of -10)², which is 25, then subtract it:
f(x)=x²-10x+25-25+16
f(x)=(x-5)²-9
so the vertex is at (5,-9)
another way to do it:
f(x)=x²-10x+16
the vertex is when x=-

, b=-10, a=1 in this case.
x=-(-10/2*1)=5
plug x=5 into the quadratic function, you get f(x)=-9
The range of the top plot, hours spent by 13-15 year olds, is found by subtracting the highest value, 34, and the lowest value, 21. 34-21=13.
The mean of the top plot is found by adding together all of the data points and dividing by 10 (the number of data points):

The range of the bottom plot, minutes spent online by 16-18 year olds, is found by subtracting the highest value, 36, and the lowest value, 12. 36-12=24.
The mean of the bottom plot is found by adding together all of the data points and dividing by 11 (the number of data points):