1 + (-5) becomes 1 - 5 because you are adding a negative number.
1 - 5 is -4
If you would like to know if (3, 6) is a solution to the inequality x + y <= 9, you can calculate this using the following steps:
(3, 6) ... x = 3, y = 6
x + y <= 9
3 + 6 <= 9
9 <= 9
Result: (3, 6) is a solution to the inequality x + y <= 9.
