Final answer:
To plot the first addend and the sum on the number line, locate the first addend and mark a point. Then, add the second addend to the first addend and mark a point at the new location.
Step-by-step explanation:
To plot the first addend and the sum on the number line, we start by locating the first addend, which is 3.8. We mark a point at 3.8 on the number line. Then, we add the second addend, which is -0.6, to the first addend. Since -0.6 is negative, we move 0.6 units to the left from 3.8 to find the sum. We mark a point at this new location on the number line. So, the first addend is plotted at 3.8 and the sum is plotted at 3.2.