How do you check 16 + 4y equals 40 with subtraction ​

Aclass consists of 55% boys and 45% girls. it is observed that 25% of the class are boys and scored an a on the test, and 35% of the class are girls and scored an a on the test. if a student is chosen at random and is found to be a girl, the probability that the student scored an ais

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Ihave trouble finding the nth term of a linear sequence