If y products are defective, the proportion of defects is y/x. So the proportion of acceptable products is 1-y/x. The probability of selecting one acceptable product is p=1-y/x. The probability of selecting 10 acceptable products is p^10 or (1-y/x)^10.
[If x=10,000 and y=200, then p=0.98 and the probability of selecting 10 acceptable products is 0.817 or about 82%.]