I was really scratching my head because I have the 6 equations. I'm good at solving equations and I was questioning my sanity here; if I can solve 5 equations out of 6, the last one will be a child's play. I saw the "X" but really thought the equation was not complete so I completed it in my head. I was still in equation solving mode. I completed it to have the same result because I was multiplying by the same d'ni numeral. Now, I know what has to be multiplied!
Now that I get it, I will gladly go with confidence, open that open door, and end up in a dead end!
I already know my fate.
At least, I learnt 2 lessons in your latest age: look everywhere (ref. 7th cloth) and don't assume it is an equation even thought it seems at first glance (ref. door code).
Thank you for this great installment in your ever expanding series of ages!
Looking for the next one, I hope the monster won't follow our trails...