could you explain the logic behind this working:
(x-1)/x = sqrt 36/49
or x = 7
for a die with x sides, to not get a particular number (say 4)
= 1 - [1(x-1) + (x-1)1 + 1)] / x^2
=> (x-1)^2/x^2 = 36/49
and n = 7
But, a very quicker way, I saw "49" in the denominator and "two rolls" (which requires x^2 in denominator), so decided it should be 7.