Some examples for the formula
The format of the equation that shows you where the vertex is
y = a(x - h)2 + k
Example. This parabola has a vertex at (3,4).
y = 2(x - 3)2 + 4
Example 2. This parabola has...

Two sweaters for $27.04 means each one costs 13.52 (half of the total)
$13.52
x 6
______
$81.12
You are correct.
Or to solve it with algebra
Set up a relationship with the two quanties and an unknown...

One to one
If you can draw a horizontal line that crosses the graph in more than one place, then the function is NOT one to one. For example, a parabola is a u-shaped graph. You can cross the graph in two places. Any straight line is a one to one graph.

t is 4 more than the product of 7 and s
t = 4 + 7s

(2x+1/3)-(x-5/4)=1/2
It looks like there is a confusion about the parenthesis.
Start by distributing the negative sign ("remove" the negative)
2x + 1/3 - x + 5/4 = 1/2
Combine like terms, the x's.
x...

-5(b-4)
-5b + 20 is the answer
Other examples of distributive problems:
2(x+y)
2x + 2y
9(3+2)
27 + 18
-8(x - y)
-8x + 8y (notice that the two negative signs...

The rate is a fraction of cups per people.
10 cups / 4 people
10/4
10/4 is reduced to 5/2.
Sometimes people write the rate as a ratio like this 5:2