Answer:

And the width for this case is:

And we know that the perimeter is given by:

And replacing we got:

And symplifying we got:

Step-by-step explanation:
For this problem we know that the lenght of the rectangle is given by:

And the width for this case is:

And we know that the perimeter is given by:

And replacing we got:

And symplifying we got:

Seems like you already have the answer so peace
Answer:
y=3-3/4x
Step-by-step explanation:
3x+4y=12
-3x -3x
4y=12-3x
/4 /4
y=3-3/4x