What is the exact volume of a sphere that has a radius of 7.5 ft?

Which equation and solution can be used to solve this problem? thirteen less than a number is sixteen. 13-n=16: add 13 to both sides. the answer is 29. n+13=16: subtract 13 from both sides. the answer is 3. n+16=13 subtract 13 from both sides. the answer is 3. n-13=16: add 13 to both sides. the answer is 29.

In the coordinate plan (-6,9) b (3,9) c (3,3) def is shown in the coordinate plan below

Twice the sum of a number and 4 is equal to three times the difference of the number and 7. find the number.