let the uniform width be x inches
length of frame=12+2x inches
width of frame=8+2x inches
Area of frame=(12+2x)(8+2x)=192
96+24x+16x+4x^2=192
4x^2+40x-96=0
x^2+10x-24=0
(x+12)(x-2)=0
x=-12 (width cant be negative)
or
x=2
Width of the frame is 2 inches