HELP ME I WILL FAIL plz

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

Aword processing program requires a 7- digit registration code made up of the digits 1,2,4,5,6,7 and 9 each number has to be used and no number can be used mor than once how many codes are possible

What is the 17th term in the arithmetic sequence in which a6 is 101 and a9 is 83