What type of characteristics would you expect from the following? Choose 3 (thank you in advance)

8.98 dm3 of hydrogen gas is collected at 38.8 °c. find the volume the gas will occupy at -39.9 °c if the pressure remains constant.

Sum of brother and sisters age is 26. four times the brothers age is subtracted from three times the sisters age, the difference is 8. what are the ages of the brother and sister?

I’m an electrically neutral atomic any element, there are equal numbers of