Answer
a)
The $x$-intercept is $3$.
The $y$-intercept is $10.5$.
b) See the graph below.
Work Step by Step
a)
In order to find the $x$-intercept, let $y=0$ and we have to solve the equation.
$7x+2y=21$
$7x+2(0)=21$
$7x=21$
$x=3$
The $x$-intercept is $3$ and the point $(3,0)$ is on the line.
In order to find the $y$-intercept, let $x=0$ and we have to solve the equation.
$7x+2y=21$
$7(0)+2y=21$
$2y=21$
$y=10.5$
The $y$-intercept is $10.5$ and the point $(0,10.5)$ is on the line.
b) In order to sketch the line, we only have to plot the intercepts then connect them using a line.