You may wantto dig into the Configurations/Design Table section of the forum for Equations.
If you sinply want to LINK one dimension to Equal another, the function is called LINK.
If you want to get more complicated, you'd be looking at EQUATIONS.
I hope this doesn't come across as being bursque, I find that I learn best by doing rather than following.
Jumping from CAD to CAD, names changes while functions remain similar. Knowing what something is called withing the framework can be key.
For your first dimension, use linked dimensions, as Alan and Scott suggested. For the second, I usually just use sketch relations, as they seem more robust and easier to use than equations. If you have an irregular outline, you may need to add some construction lines as well.Sometimes it is nice to put in construction lines just to make it easier for someone coming along later to understand.