width with unknown variable

[cmorton557]

The length of a rectangular label is 3 centimeters less than twice the width. The perimeter is 54 centimeters. Find the Width. Define your work with the unknown quantities in terms of variable. Please help. I don't even know where to begin.

[Guest]

Lets length-a,width-b. The two sentences turned into equations.

[tex]\begin{array}{|l} a+3=2b \\ 2(a+b)=54 /:2 \end{array}[/tex]

[tex]\begin{array}{|l} a=2b-3 (we- are- replacing)\\ a+b=27 \end{array}[/tex]

2b-3+b=27 [tex]\Leftrightarrow[/tex] b=10 ;we know a=2b-3 [tex]\Leftrightarrow[/tex] a=2.10-3=17
a=17 centimeters ;b=10 centimeters