The strategy I don't, but the answer is 7,141
<u>Answer</u>:
x = 7, y = 2
<u>Explanation</u>:
equations given:
x + 7y = 21
x + 4y = 15
make "x" the subject:
x + 7y = 21
x = 21 - 7y .........equation 1
x + 4y = 15
x = 15 - 4y .......equation 2
Solving both the equations simultaneously:
15 - 4y = 21 - 7y
-4y + 7y = 21 - 15
3y = 6
y = 6 ÷ 3
y = 2
If y is 2
Then x = 21 -7y;
x = 21 - 7(2)
x = 21 - 14
x = 7
Is there a picture to go along with this?
Answer:




With 



So then the x intercept would be (0,-5). And finally we can graph the function as we can see in the figure attached.
Step-by-step explanation:
For this case we know the following function:

We can begin the zeros or the values where the function is 0 like this:

And solving for x we got:

Now we can rewrite the expression like this:

And we can find the position for the vertex at x with this formula:

With 
And replacing we got:

And then with the coordinate of x for the vertex we can find the coordinate of y replacing the value of x obtained for the vertex.

Then we can find the intercept using the value of x=0 and replacing into the function we got:

So then the x intercept would be (0,-5). And finally we can graph the function as we can see in the figure attached.