Here is the tutorial.
Draw a center point rectangle at origin. Smart Dimension one side.
Smart Dimension other side and in value input press =.
Select the 1st dimension and then *0.75. This will be expression y=0.75*x.
Draw a circle at origin and smart dimension by the first dimension /3. i.e.z=x/3.
Double click the part. It will show all the dimensions.
Double click the extrusion dimension and it's relation with the height of part also *1.25. i.e. a=1.25*x.
When we change the height of part from 100 to 150.
Click Rebuild and we have new dimensions.