The fastest pizza box folder can assemble 8 pizza boxes in 21 seconds. At this rate, how long would it take to assemble 20 pizza boxes?

\( \left(C_{f}\right), f(x)=x-3+\frac{8 x}{3 x^{2}+1} \) :

3. Let \( R \) be a commutative ring with unity, where \( a, b \in R, 0_{R} \) be the zero element in \( R \) such that \( a \in R \) is a unit and \( b^{2}=0_{R} \). Then show that \( a+b \in R \) is also a unit in \( R \).

Question \( \angle 1 \) and \( \angle 2 \) are complementary angles. If \( \mathrm{m} \angle 1=(5 x+25)^{\circ} \) and \( \mathrm{m} \angle 2=(6 x-1)^{\circ} \), then find the measure of \( \angle 1 \).

\( \frac { a } { \beta } + \frac { \beta } { \alpha } \geq 2 \)

\begin{tabular}{l} Angles 5 and 8 are... \\ Alternate Interior Angles \\ Same Side Interior Angles \\ A Lame Side Exterior Angles \\ Vertical Angles \\ \hline Alternate Exterior Angles \\ \hline Corresponding Angles \\ \hline\end{tabular}