There is no formula for finding prime numbers. The rule is just if a number is prime then it is divisible by 1 and itself
Where is the list will all of this the list is needed
If you spent 80% that means you have 20% left, we'll use B as variable
20% x B = 12
0.20/0.20 x B = 12/0.20
B = 60
24) All percents are numbers with the decimal moved 2 to the right. So if you have 275%, move the decimal to the left twice to get a factor of 2.75. that means that the puppy is 2.75 times heavier at 4 months than it was at 2 months. Since you need the answer as a mixed fraction, your answer is;

28) If 6 of 75 trees are 30+ feet tall and you need to know how many are under, subtract 6 from 75 to get (75 - 6) = 69 trees under 30ft tall.
You're looking for the percent of trees under 30ft tall, so divide the number of trees <30ft by the total number of trees to get;

Move the decimal 2 to the right to get
92%.
Your answer is that
92% of trees is under 30ft.