Question 991004
.
Let &nbsp;<B>x</B>&nbsp; be the length in centimeters, &nbsp;and &nbsp;<B>y</B>&nbsp; be the width in centimeters.


You have two equations


{{{system(x = 3y,
xy = 108)}}}.


Substitute the expression for &nbsp;<B>x</B>&nbsp; from the first equation to the second one. &nbsp;You will get


{{{3y^2}}} = {{{108}}},


{{{y^2}}} = {{{108/3}}} = 36,


y = +/- 6.


Only positive value suits. &nbsp;Thus the width is &nbsp;6 cm.


Hence, &nbsp;the length is 3*6 = 18 cm.


<U>Check</U>. &nbsp;18*6 = 108 {{{cm^2}}}.