My dog was born when I was 15 years old. Two years from now, my dog will turn 4 years old. How old am I now? Think carefully first, then make a decision:
In 2 years, my dog will be 4 years old, so my dog is 4 - 2 = 2 years old now. So I am 15 + 2 = 17 years old now. So, the answer is 17.