Let's label the number you're trying to find x. You have to set up a system of equations.
1. Five times a number can be labeled as 5x.
2. Subtracted from 20 gives us 5x-20.
3. The problem says this is the same as simply tripling the original number. So set the first equation equal to 3x.
4. 5x-20=3x
5. Move like terms onto the same side. We can do this by subtracting 3x from both sides and adding 20 to both sides.
6. 5x-3x=20
7. 2x=20
8. Divide both sides by 2 to get x by itself.
Answer: x=10
