1. The problem involves understanding the expression for the integrand given as $2x = 2 \times 1 = 2$ and then interpreting $2x = 2t$. 2. First, the integrand is the function inside an integral that we are integrating with respect to a variable. 3. In the expression $2x = 2 \times 1 = 2$, it shows substituting $x=1$ into $2x$, resulting in $2 \times 1 = 2$. 4. The second expression $2x = 2t$ suggests replacing the variable $x$ with $t$, so the integrand becomes $2t$. 5. This means the integrand is a linear function of the variable, either $2x$ or $2t$, depending on the variable of integration. 6. To summarize, the integrand $2x$ evaluated at $x=1$ is 2, and if the variable changes to $t$, the integrand is $2t$. Final answer: The integrand is $2x$ or equivalently $2t$ depending on the variable, and evaluating at $x=1$ gives 2.