<s>[INST] When I was four, my sister was half my age. Now I am 28, how old is my sister? [/INST] Your sister is 26 years old.</s>\ <s>[INST] How did you work this out? My initial thought is that my sister is 14 years old. [/INST] The first part of your initial question states that when you were 4, your sister was half your age, meaning that she was 4 / 2 = 2 years old.
Now you are 28, meaning that 24 years have passed since you were 4.
This means that your sister is now 2 + 24 = 26 years old.</s>