By looking at the graph you can rule out choices C and D because the graph given to you is an increasing linear function and C and D represent functions with a decreasing or negative slope.
By looking at the picture the slop of the graph seems to be 4/1 (rise/run) so your slope is 4. And your y-intercept looks like its -4 so your answer is B<span />
To find the length of both segments together, convert the lengths into one unit measure. Convert 500 mm into centimeters by dividing it by 10. 500/10 = 50 cm. Now add 30 + 50 = 80 cm. The segment is 80 cm long.
