Question 23506
Draw the picture of the original garden with 
width = 4 and length = 12
Draw a uniform border around three sides having
a uniform width of "x".
The new width is now 4+x; the new length is now 12 + 2x
The new area is (4+x)(12+2x) = 96
         48+20x+2x^2 = 96
        2x^2+20x-48=0
         x^2+10x-24=0
        (x+12)(x-2)=0
Therefore x=2 meters is the uniform width of the border.

Cheers,
Stan H.