Answer:
The area of a rectangle is the length multiplied by its breadth.
Since the length is [tex]3(n-1)[/tex] and the breadth is [tex]n+2[/tex] and the area is 54, you can form an equation as followed:
[tex]3(n-1)*n+2=54[/tex]
[tex]3n(n-1)+2=54[/tex]
Expand:
[tex](3n*n)-(3n*1)+2=54[/tex]
[tex]3n^2-3n+2=54[/tex]
Subtract both sides by 54:
[tex]3n^2-3n+2-54=54-54[/tex]
[tex]3n^2-3n-52=0[/tex]
