The y-intercept would be (0, 13)
Step-by-step explanation:
The equation for the slope-intercept is y =3x-4
To solve this problem you must apply the proccedure shown below:
1- The formula for calculate the area of this rectangle is:

Where
is the length and
is the heigth.
2. Let's call identify the heigth with the variable
.
3. If the length is
longer than the heigth, you have:

4. Therefore, you can write the following polynomial expression:

5. If you know the value of the heigth, you can susbstitute it into the polynomial expression shown above and you will obtain the area.
Therefore, the answer is: 
Btw I’m not 100% confident in this answer.
There is a open circle over 7 in the x-axis b cause it is not greater than and less than 7