Answer plz. ill mark brainleist

What is the common difference in the following arithmetic sequence 7,3,-1,-5

With these: 18/36 = 1/? missing number change 1 5/8 to improper fraction. change 19/5 to a mixed number.

Aclassroom is made up of 11 boys and 14 girls. the teacher has four main classroom responsibilities that she wants to hand out to four different students (one for each of the four students). if the teacher chooses 4 of the students at random, then what is the probability that the four students chosen to complete the responsibilities will be all boys?