Answer:
Step-by-step explanation:
Area=Length x Width
So you start with what you know
Length or in this case height=4x
Width=3x+1
Now you just plug it in
A=4x(3x+1)
Distribute the 4x to both terms (3x & 1)
A=12x^2+4x
Since we do not know what x is that would be your simplified answer.
