In order to answer this, you need to find the equation of the line. The equation of a line is y= mx + b; mx being the slope and b being the y- intercept. The y intercept is located at (0, 20).
To find the slope, take two points. Let's use (1,40) and (2,60).
Use the slope formula: (y1 - y2)/(x1 - x2)
(60-40)/(2-1)= 20/1= 20.
The slope is 20, the equation is: y = 20x + 20.
Now plug 10 into x:
y = 20(10) + 20
y = 220
Your answer is 220.