Step 1: Identify the matrix J. J = [[1, 2, 1], [0, 1, 3], [2, 1, 0]].
Step 2: Write down the formula for the determinant of a 3x3 matrix: det(J) = a(ei - fh) - b(di - fg) + c(dh - eg), where the matrix is: [[a, b, c], [d, e, f], [g, h, i]].
Step 3: Assign values from matrix J to the variables: a = 1, b = 2, c = 1, d = 0, e = 1, f = 3, g = 2, h = 1, i = 0.
Step 4: Calculate ei - fh: ei = 1*0 = 0 and fh = 3*1 = 3, so ei - fh = 0 - 3 = -3.
Step 5: Calculate di - fg: di = 0*0 = 0 and fg = 3*2 = 6, so di - fg = 0 - 6 = -6.