Set 1: Linear Equations

Choice C is correct. Choice D is the correct answer. 1. Start with the equation: $7x + 21 = 42$ 2. Subtract 21 from both sides: $7x = 42 - 21$ 3. Simplify: $7x = 21$ 4. Divide both sides by 7: $x = \frac{21}{7}$ 5. Simplify: $x = 3$ 6. Verify: $7(3) + 21 = 21 + 21 = 42$ ✓ Choice C is incorrect because this results from adding 21 to 42: $63$, then $63 /7 = 9$. Wrong inverse operation. Choice C is incorrect because this is the value of $7x$. You need to divide by 7. Choice D is incorrect because this results from multiplying 21 by 7: $147$.