Dmitry B. answered • 04/07/20
Five years of Prealgebra tutoring at a math group
The best way to help you is to find out what exactly you don't understand. This way we can see where the gap is and help you to liquidate that gap. However because you didn't give any details what have you tried (try this next time, you will benefit of this) and what went wrong I have no way to know this.
The problem is clear, you need to find dimensions (width and height) of a poster. There is an assumption that it is rectangle, I think it is a fair assumption. What do you know about a rectangle?
Area = w × h
Perimeter = 2 × (w + h)
where w = width, h = height.
So, you have 2 equations:
18 = w × h
18 = 2 × (w + h)
Second equation gives you a value of "w" in terms of "h": w = 9 - h.
Now substitute this into a first equation and you will get: 18 = (9-h)*h. Solve this for h:
h**2 - 9 * h + 18 = 0
D = 81 - 4 * 1* 18 = 9
h = 3 or 6.
If h= 3, w= 6 or h=6, w= 3. Thus dimension of this poster could be 3 x 6 or 6 x 3.
