1) This is not a linear equation as it curves and thus has acceleration and thus its velocity is not constant. You COULD find a linear least squares equation, but I do not think that that is what they want you to do, and the least squares regression is still only an approximation...so I would say that you cannot write a linear equation for the graph.
2) The y-intercept is the value of y when x=0, and this point is clearly marked as the point (0,1)
3) The slope of a line can be found using any two points on the line and it will be equal to:
m=slope=(y2-y1)/(x2-x1)...in this case:
m=(2-1)/(2--3)=1/5 so the line has a slope of 1/5
4) To find the y-intercept precisely we start with the slope that we found earlier and use that value in the slope-intercept form of a line, y=mx+b, and since m=1/5 we have:
y=x/5+b, where b is the y-intercept and using (2,2) we can solve for b...
2=2/5+b
10/5=2/5+b
b=8/5 or if you prefer 1 3/5 or 1.6
So the y-intercept is 8/5, 1 3/5, or 1.6 depending on how you'd like to use it.
5) We have already found b and m of the y=mx+b so the equation of this line is:
Subtract 19 from 39
Divide by 4