Question 939392
let  x be the width of rectangle

the length of rectangle is 1cm less than twice the width
  length  =  2*x-1
perimeter  = 28
   formula: perimeter   = 2(length+width)
            28 = 2((2x-1)+x)
              28 = 2(2x-1+x)
               28 = 2(3x-1)
    divide with 2 on both sides
          {{{28/2 = 2(3x-1)/2}}}
                {{{14  = 3x-1}}}
 add 1  on both sides
  14+1 = 3x-1+1
 15 = 3x
 divide with 3 on both sides
 {{{ 15/3   = 3x/3}}}
 {{{5 =x}}}
 width  =  5 cm
length  =  2*5 -1
            = 10-1
                = 9 cm
 Length  = 9 cm
Result : Dimensions: length  = 9 cm & width  =  5 cm