To ensure they are there for posterity's sake.
Well first you would add 5 to both sides making it look like 3x -5(+5)=10 + 5 you would do this to get X on its own and so that makes the new equation 3x=15 and then you devide both sides by 3. (3x÷3=15÷3). which equals x=5
The epoch that we are currently living in is called the Holocene epoch of the qauternary period.