Naledi buys 5 packets, each containing 12 items. Every item is sold for R2, and the total profit is R30. Let x be the cost of one packet. Which equation models the situation?

To verify a proposed solution to an equation, substitute the proposed value into the original equation and check if both sides are equal.
The equation is $3x + 5 = 29$, and the proposed solution is $x = 8$.
Substitute $x=8$ into the left side of the equation:

$$3(8) + 5 = 24 + 5 = 29$$

Since the left side (29) equals the right side (29), the proposed solution $x=8$ is correct.

The correct calculation is $\boxed{\text{D. } 3(8)+5= 29; \text{ both sides have the same value, so } x = 8 \text{ satisfies the equation}}$.

Andile's model is $7 + x + 4 = 60$.
The problem states "7 equal boxes of $x$ pencils". This means $7 \times x$, or $7x$, not $7 + x$. The learner is incorrectly treating multiplication as addition. The correct model should be $7x + 4 = 60$.

The response that best diagnoses and repairs the model is $\boxed{\text{A. The learner treated 7 equal groups as addition; write } 7x + 4 = 60 \text{ and connect } 7x \text{ to repeated groups}}$.