Strings: Level 2 Challenges Practice Problems Online

How many times does the number '7' appear in String a?

String a = "1628261829271628239271982027282927827618227261434335242627282928276272728292918972625252728921011514252431524251524152524254253435241534223392028302029382002929102102929101192928101019298281910101010991929121900101010292991010101029920101092929128919010101929928912910101828272663272818182726256352562615624236252377777215252616252541256625421652392029281710000001010929298282781818288272718821827271288182712819889192919818991292191212272726167172762626216163515251.";

Count the total number of letter "F" in the following text:

FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS...

This teaser is called "Alzheimer's' eye test".

Consider the calculation as follows :

$\frac{2(X+3)} {Y+9}$ (where X & Y are variables)

Which of the following represents the correct Reverse Polish notation for that calculation :

A 2 X * 3 + Y / 9 +
B 2 X 3 + * Y 9 + /
C 2 X + 3 * Y 9 + /

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Strings: Level 2 Challenges