Question 64023
The area of a rectangle is given by:
{{{A = L*W}}} 
In your rectangle: {{{L = 3W}}}
If you decrease the length, L, and the width, W, each by 2 cm, the area, A, is decreased by 36 sq.cm.  So, puting this into an equation, you'll get:
{{{(L-2)(W-2) = A-36}}} Substituting 3W for L, and L*W for A, you now have:
{{{(3W-2)(W-2) = 3W^2-36}}} Simplifying this, you'll get:
{{{3W^2-8W+4 = 3W^2 - 36}}} Further simplification yields:
{{{-8W+4 = -36}}} and:
{{{-8W = -40}}} Dividing by -8:
{{{W = 5}}} and
{{{L = 3W}}} so:
{{{L = 15}}}

The original length, L = 15 cm
The original width, W = 5 cm

Check:
Original area:
{{{A1 = (15)(5)}}}
{{{A1 = 75 cm^2}}}

After decreasing the lenth and width by 2 cm:
{{{A2 = (13)(3)}}}
{{{A2 = 39}}} sq.cm.

The decrease in area is:
{{{75-39 = 36}}}sq.cm.