Question

3 + d < 3 – d. Solve

Answer 1

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.