Question 343968
NEED TO KNOW:
PERIMETER IS THE TOTAL LENGTH OF ALL FOUR SIDES

LET "L" REPRESENT THE LENGTH OF THE BASE AND "H" BE THE HEIGHT OF THE RECTANGLE
ACCORDING TO THE QUESTION, THE FOLLOWING IS TRUE.
{{{L=3*H}}}
TOTAL LENGTH OF ALL FOUR SIDES IS 72cm
{{{L+L+H+H=72cm}}}
SUBSTITUTE FOR L
{{{(3*H)+(3*H)+H+H=72cm}}}
SOLVE:
SIMPLIFY:
{{{8H=72cm}}}
DIVIDE BOTH SIDES OF THE EQUATION BY 8
{{{H=highlight(9cm)}}}
{{{L=3*9cm}}}
{{{L=highlight(27cm)}}}

check your answer!!
{{{27cm+27cm+9cm+9cm=72cm}}}