Blood alcohol content, reflex time for a single person

Some boys and girls were asked if they had a pet. one third of the group were boys. there were 20 boys. 20% of the girls had a pet. boys with a pet : girls with a pet = 1 : 5 i need to know how many girls there are.

Which of the following is the inverse of y = 3∧x y = 1/3∧x y = ㏒3x y = (1/3) ∧x y = ㏒ 1/3∧x

Aconstruction worker has rope 9 m long he needs to cut it in pieces that are each 3 /5 m long how many such pieces can he cut without having any rope leftover?