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
Merge pull request #53302 from mauk81/refactoring

removed unused variable AND_TEXT
Fix duplicate choices in trigonometry_1

trigonometry_1.html?seed=9&problem=cosTrig1 was broken because of MathJax inconsistently running sometimes before the answers were compared. Instead, run only tmpl first and always run the other modules afterwards.

Test Plan:
trigonometry_1.html?seed=9&problem=cosTrig1 shows three unique answers.

Auditors: emily

CC: eater
Make less awkward i18n in lcm_gcd_word problems

Summary:
By using a bunch of nested ifs, recombine some of the sentences
originally split up for i18n, to make the sentences work better. Also, use a
table for styling in one section so that it appears correctly in the exercise
regardless of width.

Test Plan:
Open
`/exercises/least_common_multiple_and_greatest_common_divisor_word_problems.html`
in local mode. See that the hints in all the problem types have sentences like
"1 set with 40 pencils and 20 folders" and not "There is 1 set. It has 40
pencils. It also has 20 folders". See that the comparison between the two
different groups are next to each other.

Reviewers: alpert, eater

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D3002
Fix "I don't know this button" for mastery tasks

Summary:
Prior to this change, clicking "I don't know this" button sent up the
request to the server for the *following* exercise.

Test Plan:
Open a mastery task
in JS console, check exercise name via Exercises.currentCard.attributes.exerciseName
Click "I don't know this", verify in Network tab that XHR is for the right exercise
Do the same for an assessment task

Reviewers: james, mattdunnrankin, alpert

Reviewed By: alpert

CC: marcia, alpert

Differential Revision: http://phabricator.khanacademy.org/D3026
Typeset direct code children (for multiple, etc)

Test Plan:
scientific_notation.html?debug&problem=0&seed=56 shows the "x 10".

Auditors: emily
removed multiple equal sign, fix: #53691
fix rounding in hint, fix #53771

no rounding to the ten thousandth before rounding to the thousandth.
example: *1/22 = .04545* should be rounded from *.0454* not from *.0455*
Merge pull request #53842 from mauk81/patch-4

fix rounding in hint, fix #53771
Change selector for new location of style el

Goes with rWE3304e88aaf5df4ddbedeb9214d781cc3381aa964.

Auditors: benkomalo
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