Find the length of side x in simplest radical form with a rational denominator

Ineed solving this problem h/8=-25 solve for h idk how to this can someone show me and also give an answer you

According to modern science, earth is about 4.5 billion years old and written human history extends back about 10,000 years. suppose the entire history of earth is represented with a 10-meter-long timeline, with the birth of earth on one end and today at the other end.

Alex measured the length of an item to be 3.7 cm. the actual length is 3.5 cm. what is alex’s percent error?