fix plural in problem text, fix #47643

*isSingular(randRange( 1, 8 ))* and *<var>randRange( 1, 8 )</var> hour/s* are different numbers. i added a new variable *sleddingHours* and use it as *<var>sleddingHours</var> <var>plural("hour", sleddingHours)</var>*
avoiding rounding problem, fix #46111 and #49683

calculate with fraction like the hint instead of decimals.
39.9/12*60=199.49999999999997 is now 133/40*60=199.5
102.66666666666666/32*60=192.49999999999997 is now 77/24*60=192.5
fix wording in geometry_proofs_intro
removed multiple equal sign, fix: #53691
Merge pull request #52187 from mauk81/patch-2

fix plural in problem text, fix #47643
Merge pull request #52272 from mauk81/patch-5

avoiding rounding problem, fix #46111; fix #49683; fix #52739
Merge pull request #52393 from mauk81/congruent

fix wording in geometry_proofs_intro
Merge pull request #53732 from mauk81/patch-1

removed multiple equal sign, fix: #53691
Merge remote-tracking branch 'upstream/master'