Question 865961
The first two sentences can give the dimensions.  

x and y dimensions, x is length.
{{{x=3y+6}}}.
{{{xy=45}}}
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{{{(3y+6)y=45}}}
{{{3y^2+6y-45=0}}}
{{{y^2+2y-15=0}}}
{{{(y-3)(y+5)=0}}}
{{{highlight(y=3)}}} and {{{3*3+6=highlight(x=15)}}}.
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The diagonal is a hypotenuse of a right triangle of the rectangle's sides.
{{{sqrt(3^3+15^2)}}}
{{{sqrt(9+225)}}}
{{{highlight(sqr(234)=15.3)}}}...