Help please

a) No boy  probability = (1*1*1*1)/ (2*2*2*2)= 1/16

Atleat one boy = 1-1/16 = 15/16

but 2nd answer how will you calculate ?-----------------------------

b) in a above there includes a chance that there can be 4 boys

So, if we reduce this probability of getting 4 boys that is 1/16 out of a), then there will atleast be one girl & one boy = 15/16 - 1/16 = 14/16= 7/8 

thank u so much.*************