78 9 10 11 12 13 14 15 plz that is all but i don't get it and my math teacher sucks so when you tell me the answers can you show me how you did it or at least what i'm doing plz plz plz plz or not but i need the answers

The formula for area is pi x r^2 (pi times radius squared) so, for number 7 youre given the radius or "r", which is half the length of the inside of the cirlce. On a calculator: you would do 8 times 8 (8^2) because that's the radius squared and then you should get 64 and times 64 by 3.14 or use the pi button depending on what your teacher prefers you to use. 

When you're given diameter or "d" which represents the is equal to the radius times 2. So, for example, number 8 the diameter is 26 so, the radius is 13. Use the formula for area just like in number 7 to find the area of this circle. 

Make sure you pay attention to what information youre given (whether its "d", Diameter, "r" or radius. Use those two lists of steps for solving numbers 7 through 12. 

For numbers 13-15: use the number (22/7) instead of 3.14 or the pi button on your calculator and do the same steps

Let me know if you still need help after this:) happy math solving!