The total surface area of a rectangular prism is given by the formula:
2lw + 2lh + 2wh
Given that one face has an area of 6 in^2, 12 in^2 and 9 in^2, we can deduce the dimensions of the prism.
Let's assume the length(l) = 1, width(w) = 2 and height(h) = 3. Then the total surface area is:
2(1*2) + 2(1*3) + 2(2*3) = 4 + 6 + 12 = 22 in^2
So, the total surface area of Jillian's prism is 22 in^2.