I don’t know how to begin or solve this problem.

Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. if an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite

What is the bill of rights listed in, order

During which era in earth's history were the first insects? mesozoic precambrian cenozoic paleozoic