10. Set up a proportion and use it to solve for x.
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Tree diagram to find the prime factors of 18

(a) (8%) compute the probability of an even integer among the 100 integers 1! , 2! , 3! , until 100! (here n! is n factorial or n*(n-1)*(n-2) *… 1) (b) (16%) compute the probability of an even integer among the 100 integers: 1, 1+2, 1+2+3, 1+2+3+4, …., 1+2+3+… + 99, and 1+2+3+… + 100

Find the number of positive three-digit even integers whose digits are among 9, 8, 7,5, 3, and 1.