Well 21 times 2 is 42 and 1/3 of 21 is 7 so 42+7 is 49. hope this is right
So you would have -20C. Then you would multiply that by 1.8 which would give you -36 then you would add 32 which gives you your final answer which is -4 F
Each child has a 50% chance to be a girl and 50%chance to be a boy so with 4 children the probability is