This can be solved in steps!
1. Subtract 15 from both sides
15 + 3x < -3
→ 3x < -18
2. Divide both sides by 3
3x < 18
→ x < 6
3. Switch signs (since we divided)
x < 6
→ x > 6
4. Answer Recap
Our answer is:
→ x > 6
On a number line, this would be graphed by plotting a point at 6 (with a closed circle) and drawing an arrow that goes to the right showing that the unknown value is greater than 6.