See a possible duplicate of this question here (How to move an existing line to a parallel offset of another existing polyline) and my answer.
You can achieve this with the COGO toolbar.
Within the editing tool bar you can also create a new feature and specify the angle and length of the segment.
If you have the COGO editing toolbar available to you there is a tool called:
you could also edit your sketch properties by +/- the specified distance (more math).
The Copying Parallel Features might be of interest to you. From the help: "Copy Parallel makes a copy of selected lines at a distance you specify. You can choose to copy the new lines to the left, right, or both sides of the selected lines. You can use the Copy Parallel command, for example, to create a street centerline or a gas line that runs parallel to a road"