Awoman has 7 keys. only one of them will open her door. when seh arrives at the door there is no sufficient light for her to find the correct key. if she tries one key at a time and discards the keys that don't work, what is the probability that she will open the door with the first key she picks? what is the probability that it will take exactly three attempts to open the door? suppose that the first three attempts to open the door have been unsuccessful. what is the probability that she will pick the right key the fourth time?

answer: 2/4

step-by-step explanation:

mr. flanders’ class sold 47 doughnuts and   mr. rodriquez’s class sold 38 cartons of milk

step-by-step explanation:

let x be the number of doughnuts sold by mr. flanders’ class and y be the number of cartons sold by mr. rodriquez’s class.

1. together, the classes sold 85 items, then

x+y=85.

2. both classes earn earned $104.49 for their school. if doughnuts were sold for $1.35 each, then x doughnuts costed $1.35x. if cartons of milk were sold for $1.08 each, then y cartons costed $1.08y. hence,

1.35x+1.08y=104.49.

3. solve the system of two equations: