step 1
we have the equation
y=7x
This is the equation of a line that passes through the origin (0,0)
To graph a line we need at least two points
so
assume any value of x and then calculate the value of y
For x=2
y=7(2)=14
the second point is (2,14)
step 2
Graph the line
Plot the points (0,0) and (2,14)
join them to graph the line
using a graphing tool
see the figure below