Answer: C) {3, 4}
======================================================
Step-by-step explanation:
Solve the inequality for x.
5x + 4 < 29
5x < 29-4
5x < 25
x < 25/5
x < 5
I subtracted 4 from both sides (step 2). Then I divided both sides by 5 to fully isolate x (step 4). The inequality sign stays the same the entire time.
Since x < 5, this means the original set {3,4,5,6} becomes {3,4} since these values make x < 5 a true statement. In other words, we erase 5 and 6 because something like 6 < 5 is false.
That's why {3, 4} is the final answer.
---------------
An alternative method is to go through the set {3,4,5,6} and plug those items one by one into the original inequality. If you get a true result, then it's part of the answer.
Let's try x = 3
5x + 4 < 29
5(3) + 4 < 29
15+4 < 29
19 < 29
We get a true statement at the end, so x = 3 is part of the solution set. A similar story happens for x = 4 as well.
If we tried x = 5, then,
5x + 4 < 29
5(5) + 4 < 29
25 + 4 < 29
29 < 29
which is false. No number is bigger than itself (or smaller than itself). Therefore, x = 5 is crossed out of the original set. You should get a false statement for x = 6, which means we'll kick this value out as well.