I just spent 20 minutes converting the formula…
d = M-((M/2)+7)
…into…
M = 2(d+7)
I still got it baby!
(Even if it would have taken me about a 10th of the time back in high school :))
The steps are…
d = M-((M/2)+7)
M = d+((M/2)+7)
M = d+7+(M*0.5)
M-(M*0.5) = d+7 (This one took me ages)
0.5*M = d+7
M = 2(d+7)
Now, does anyone recognise the base formula?