The solution to the first part of your question is "Splitting a line into an equal number of parts":
The Split command on the Editor toolbar allows you to split a line
into an equal number of new features. For example, you can use this
Split option to break a line into pieces that are the same length.
This functionality is similar to the Divide command available in
previous ArcGIS releases.
Further down on the same page is a section on "Splitting lines proportionally". This should help you with the second part of your question, although you will need at least a Standard (ArcEditor) license to do this.
The Proportion command Proportion on the COGO toolbar splits a
selected line feature into a number of segments, based on specified
distance values. If there is a difference between the feature length
and the entered values, this difference is proportioned between all
the new segments. Proportion is useful when you are working with exact
measurements, such as COGO or survey data.
For example, you have line features that need to be split into
specific lengths. The example below shows a line feature that needs to
be split into four parts: 13.79 feet, 48 feet, 60 feet, and 60 feet.
The Proportion command is used to split this feature into the four new
As stated above, in previous versions of ArcGIS, dividing lines into segments was accomplished using the Divide command.