The is a 50% chance of being a boy or a girl.....previous siblings do not matter. Every child is an independent event. So even if u had 2 siblings that were boys, the result of the next one being a boy is still gonna be 50%...just as the odds of it being a girl, is 50% as well.
Answer:for #2 it's answer 1. #3 is " five less than twice a number is 2x-5. Then 5 times the sum of two numbers if 5x+y. The the difference of 5 and a number squared is (5-x)*2