0.78 per pound is unit rate
Since 5lbs is $3.90, 0.78 is the cost of one pound.
3.90 divided by 5 is 0.78
To find compound probability, multiply the probability of the first and second events. In this case, if you wanted to draw the green first and then the blue, 10/24 or 5/8 times 6/23 equals 30/184 which reduces to 15/92.