Réponses

2017-01-11T19:01:46+01:00
Let a be a natural number.
Double it : 2a
Add five : 2a + 5
Double this answer : 2(2a+5)=4a+10
Add two : 4a+12
Take away the number you first thought of : 4a+12-a=3a+12=3(a+4)
Your final answer will be a multiple of 3.