Omitting The Multiplication Sign And Evaluating

When substituting numbers into algebraic expressions, a very common error is misinterpreting the omitted symbol. For example, a student evaluates $3d$ for $d=6$ and writes the answer as $36$. This is incorrect because $3d$ implies a hidden sign, not simply placing the digits side-by-side. The correct calculation is $3 \times 6$, which equals . On the other hand, if we evaluate $2j$ when $j=5$, the expression is properly calculated as $2 \times 5$. The correct value for this second expression is indeed .