You will surely understand that...

A letter was left on the dining room table:

My Dear Wife, You will surely understand that I have certain needs that your 54 year old body can no longer supply. I am very happy with you and I value you as a good wife. Therefore, after reading this letter, I hope that you will not wrongly interpret the fact that I will be spending the evening with my 18 year old secretary at the Comfort Inn Hotel. Please don't be perturbed - I shall be back home before midnight.

When he came home, he found the following letter on the dining room table:

My Dear Husband, I received your letter and thank you for your honesty. I would like to take this opportunity to remind you that you are also 54 years old. At the same time I would like to inform you that while you read this, I will be at the Hotel Fiesta with Michael, my tennis coach who, like your secretary, is also 18 years old. As a successful businessman and with your excellent knowledge of math, you will understand that we are in the same situation, although with one small difference: 18 goes into 54 a lot more times than 54 goes into 18. Therefore, I will not be back before lunchtime tomorrow.