Question 941560
perimeter  = 15 feet
let x be the length of rectangular window
 width   =x/4
Perimeter  =  2 (length+width)
 {{{15=2(x+(x/4))}}}
 {{{ 15 = 2( (4x/4)+(x/4)) }}} 
 
 {{{15 = 2(4x+x)/4}}}
 {{{ 15 = 2(5x/4)}}}
 {{{ 15 = 5x/2}}}
 multiply  with 2 on both sides
 {{{ 15*2 = (5x/2)*2}}}
 {{{ 30 = 5x}}}
 divide with 5 on both sides
{{{ 30/5 = 5x/5}}}
 6=x

 
 
length (x) =  6 ft
width = x/4  =6/4
                =1.5  ft
   

Result: length  = 6 ft , width  = 1.5 ft