You have to graph it b stands for the y-intercept so on the y axis make a mark on 4 then the slope is 2 so you go from the mark up 2 to the right 1 or down 2 to the left 1 until your line crosses the x axis

The slope intercept form of equation is y=mx+b
since m=2 nd b=4 ur equation will be
y=2x+4.
Find the value of x when y=0. that value of x will be the x intercept