Answer:
Volume of original toolbox = 180 in³
Yes, doubling one dimension only would double the volume of the toolbox.
Explanation:
Volume = L x W x H
10 x 6 x 3 = 180 in³
proof:
double length = 20 x 6 x 3 = 360 in³, which is double the original
double width = 10 x 12 x 3 = 360 in³, which is double the original
double height = 10 x 6 x 6 = 360 in³, which is double the original