/sci/ - Science & Math

>>11427879
>i still don't get why it works..
The age gap between Mary and her brother never changes (it's always 12 years).
So what you have to figure out is when
Brother age * 2 = Mary's age
Since we know the difference is constant we can just rewrite Mary's age in her Brothers age
Brothers age * 2 = Brothers age + 12
Now subtract Brothers age from both sides and you will find out that he has to be 12.
(In other words if the 12 year gap has to be his age, in order for Mary to be twice his age, since Mary = Brother's age +12 = 12 + 12)


>I suck at explaining, I hope it's still understandable