Learn and practice with prime numbers divisibility rules and fractions

Learn and practice:

+ Prime and composite numbers
+ Divisibility rules (235711)
+ Prime factorization => minimum common multiple and maximum common divisor
+ Find prime numbers => Sieve of Erastothenes
+ Lowest Common Multiple (L.C.M.) and Highest Common Factor (H.C.F.)
+ Fractions:
- add/subtract fractions
- multiply fractions
- divide fractions
- compare fractions
- simplify fractions