I need help because I do not get this

What is the number 321,000,000 in scientific notation? also what is the number? ?

In a graph with several intervals o data how does a constant interval appear? what type of scenario produces a constant interval?

Pyotr tchaikovsky sporting goods operates on a 45% overhead based on the selling price, which results in an overhead of $65.34 on the newest version of an air hockey game set. if the air hockey game set costs pyotr tchaikovsky sports $49.32, find the selling price, the markup, and the net profit.