Final answer:
For all real numbers a and b, if a < b, then a < a + b < b.
Step-by-step explanation:
For all real numbers a and b, if a < b, then a < a + b < b.
To illustrate this, let's consider two numbers: a = 2 and b = 5. We know that 2 < 5, so if we add a and b, we get 2 + 5 = 7. Since 2 < 7 < 5, the statement is true.
Therefore, option 1) a < a + b < b is the correct answer.