What is this and how do i do it? (geometry)

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.

Evaluate-27 ^4/3/8 a) - 81/16 b) 81/16 c) 16/81

The parabola opens: y=√x-4 (principal square root) up down right left