What is the sum of a 12-term arithmetic sequence where the last term is 13 and the common difference is -10?

I’m confused on how to work the pie charts

Cone a has a surface area of 384 ft2 and cone b has a surface area of 96 ft? . what is the ratio of their volume?

Given that y varies directly to the square root of (x + 1), and that y = 1 when x = 8,(a)express y in terms of .x,(b)find the value of y when x = 3,(c)find the value of x when y = 5.