To solve this problem you must apply the proccedure shown below:
1. You have that
varies jointly as
and
and inversely as the product of
and
. Therefore, you can write the following equation, where
is the constant of proportionality:

2. Now, you must solve for the constant of proportionality, as following:

3. Susbtiute values:


4. Substitute the value of the constant of proportionality into the equation:

The answer is: 
Y=-1/2x+5 slope=-1/2 because it goes down one unit and to the right 2 units, and the y intercept is 5 because that's where the line intercepts the y-axis!
since the graph has direct variation as data in x axis increases y also increases.
so we need to find how many miles travelled per galloon .
we distance travelled per gallon =total distance travelled/galoons of fuel used.

for part b) slope=rise/run



slope of the graph is 2
Answer:
Step-by-step explanation:
Is this y=-x^2 +2?
Here is the graph, in the photo.
Hope you understand