Add and sub rat expr 0.5 exercise
D
Revert "D"

This reverts commit bd3627b8306f4179f9ac45d41af854f26f47b050.
Remove redundant parts of solution area
Ensure numerators never cancel
Add code for denominator simplifying to 1
Simplify solution entry further
Merge pull request #44758 from petercollingridge/sim-rat-exp-05

Adding and subtraction rational expressions 0.5