for unequal probability sampling with replacement i have an auxiliary variable that the probability of selecting an element should be proportional to but i dont know how to find what the probability would be.

eg.

element# value auxilary variable

1 12 5

2 18 3

3 25 1

how do i find what the probability of selecting say sample 1,2.

i thought it would be (5/9)*(3/9) but when add up all possible samples the probabilities dont add to one so it doesnt make sense.