Question 1031094
Set x = the original wall length
Each wall in the extended room is ( x + 15 )
So the area is ( x + 15 )( x + 15 )
( x + 15 )( x + 15 ) = 900
{{{x^2 + 30x + 225 = 900}}}
add -900 to each side
{{{x^2 + 30x - 675 = 0}}}
Factoring
(x + 45)(x - 15) = 0
So x = -45 or x = 15
We cannot have a negative length,
so the original length is 15