Question 858920
Original square is side length x.  area is x^2


New square, length increased to x+2, and implied is that this is also for a square, the area being {{{(x+2)^2=x^2+4x+4}}}.  Described further is that {{{3(x^2+4x+4)=75}}}
{{{x^2+4x+4=75/3}}}
{{{x^2+4x+4=25}}}
{{{highlight_green(x^2+4x-21=0)}}}.


Factoring that equation,
{{{(x-3)(x+7)=0}}}
One answer makes sense and one answer makes no sense.  Take the positive solution for x.
{{{highlight(highlight(x=3))}}}.  Length of the original square was 3 units.