Answer:
Well, I think we all worked with variables, but don't realise about it, because when people see these terms ''variable'', ''algebra'', they freak out.
The reality is that variables are everywhere, they are all those stuff that can variate: weigh, highness, money, population, interests, and so on.
A common problem I solved using variables is measuring time. For example, when I'm going to school I tend to calculate the time of my way.