I need some help please

In a class, there are 12 girls. if the ratio of boys to girls is 5: 4 how many boys are there in the class

Awater holding tank measures 105 m long, 50 m wide, and 8 m deep. traces of mercury have been found in the tank, with a concen- tration of 60 mg/l. what is the total mass of mercury in the tank? answer in units of kg.

Factor the expression using the gcf. the expression 21m−49n factored using the gcf