Answer
$ a.\quad$Intercepts: $(3,0)$ , $(0,10.5)$
$b.$
Work Step by Step
$\begin{array}{ll}
\text{x-intercept} & \text{y-intercept}\\
(y=0) & (x=0)\\
& \\
7x+2(0)=21 & 7(0)+2y=21\\
7x=21 & 2y=21\\
x=3 & y=10.5\\
& \\
(3,0) & (0,10.5)
\end{array}$
Draw a line through the two points.