Answer:
x > 5
Explanation:
Let's call our mysterious number as x.
2x + 5 > 15
The trick here is to solve it like a normal equation.
Subtract 5 from both sides
2x > 10
divide both sides by 2
x > 5
The values are everything above 5.
Note*: The only thing you need to know in the way I did this is to switch the sign if you're dividing by a negative.