Answer:
6,226 tiles of 9 in are needed to cover an area of 400 square feet
Step-by-step explanation:
Let
A -----> an area in square feet
t(A) ---> the total number of 9 in. tiles needed
we have

For A=400 ft^2
substitute in the equation and solve for t


That means -----> 6,226 tiles of 9 in are needed to cover an area of 400 square feet
A slope of 1/2 means for every two units to the right we move up one.
We have to be careful here because the graphs don't always use the same scale for x and y.
The bottom left uses the same scale and does indeed go two units to the right for every unit up, so that one is the answer.
Ask your self what is -2*?=23.
Then times that answer by 2.