The bag of marbles has 4 green, 2 red, 5 yellow, 1 brown, and 7 blue marbles.
Total number of marble=4+2+5+1+7=19
The probability P(E) is defined as
where n(E) is the total number of favourable events.
and n(s) is the total number of events
Hence for the given data we can write
Because total number of green marbles = n(E)=4
Total number of Marbles =n(S)=19
Hence P(E)=4/19