3 + d < 3 - d. Solve

For the sake of solving, temporarily replace the < sign with an = sign. Solve as you normally would.

3 + d = 3 - d

add d to both sides

3 + 2d = 3

Subtract 3 from both sides

2d = 0

Now replace the = sign with the < sign again.

2d < 0

Divide both sides by 2 to get your final answer.

d < 0

If you are ever uncertain with an answer to an inequality, the best thing to do is plug in a random number! (In this case, make sure the number is less than 0)

3 + (-1) < 3 - (-1)

3 - 1 < 3 + 1

2 < 4

(-1) is less than zero, and when plugged into the inequality the values of the left side is less than the value of the right side. This shows that d IS < 0.