Question

The sum of a number and 6 is at least 15

Answer 1

x>8

Explanation:

The number has to be bigger than 8 in order to be at least fifteen, so x is greater than 8

Answer 2

x + 6 ≥ 15

x ≥ 9 [subtract 6 from both sides retains sense of inequality]

To check:
Adding any number greater than or equal to 9 to the number 6 produces a result at least 15. Any number less than 9 produces a result that is not at least 15.