Question 889395
M + D = 1
D = 1.33 M
Substitute the value of D from the second equation into the first.
M + D = 1
M + (1.33M) = 1
2.33M = 1
Divide each side by 2.33
1 / 2.33 = ~  0.43
Dan gets 57% of the sub and Mike gets 43%
For a 12" sub, that's 6.84" for Dan and 5.16" for Mike.  (Approximately due to rounding.)