The value a = 4 will always yield a correct answer.
We know this by solving for a. If we do this, we will get the number needed.
a(x + 3) < 5x + 15 - x -----> simplify like terms
a(x + 3) < 4x + 15 -----> divide by x + 3
a < 4 + 3/(x + 3)
Since a is less than 4 plus a number, we know that a will always be less than 4. So we can use 4 as the number for all real solution.
