1. **State the problem:** Determine if 8 and 21 are solutions to the equation $3x = 24$. 2. **Recall the equation:** $3x = 24$ means multiply $x$ by 3 to get 24. 3. **Check if 8 is a solution:** Substitute $x=8$ into the equation: $$3 \times 8 = 24$$ Calculate: $$24 = 24$$ This is true, so 8 is a solution. 4. **Check if 21 is a solution:** Substitute $x=21$ into the equation: $$3 \times 21 = 63$$ Calculate: $$63 \neq 24$$ This is false, so 21 is not a solution. 5. **Check the addition claims:** The problem mentions $3 + 21 = 24$, but this is not the original equation. The original equation requires multiplication, not addition. **Final answer:** Only 8 is a solution because $3 \times 8 = 24$.