Me sitting here in my vans my friend bought me wondering why I’m so bored... 45 + 36 x 4 - (100^2/4) = ?

(16%) consider 3 digits integers 100 till 999. (a) (6%) compute the probability of 3 digits even number such as 100, 102, 104, etc. (b) (10%) compute the probability of a 3 digits integers with the sum of 3 digits an even integer. for example, 123 is 3 digits with sum of 3 digits even (sum =6), but 315 is 3 digits with sum of 3 digits odd (sum = 9).