Remember that when you find 30% of the number you have to subtract the 30% from your original $90 because it is 30% off the original price.
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Answer: 
Step-by-step explanation:
Given : The number of children in a family is 1, 2, 3, or 4.
Little Joe (a boy) has no brothers. But he may have sisters.
The sample space for the number of child in Joe's family : {B, BG, BGG, BGGG}, where G represents girl and B represents boys.
Then , for the probability that he is an only child, favorable outcome = B
Thus, the probability that he is an only child is given by :-

Hence, the probability that he is an only child = 
Answer: Alternate Interior Angles Theorem