Algebra

You can't, they're all prime numbers.

sqrt(49) simplifies to 7

5 + 8 is an expression that simplifies to 13

3 * 5 + 2 simplifies to 17...


... for example

I just noticed that your topic is "Algebra"

So perhaps you are looking for expressions containing pro-numerals (letters).

These expressions give the required results respectively

x + 2 = 9

2x - 10 = 16

20 - x = 3