Please help! I don't know how​

Average salary for a medical assistant is $31,220 which is a 20% income tax bracket how much money would they pay in income tax?

At his new job, jeremiah can choose an hourly rate of $9 plus a $50 weekly bonus for opening the store, or an hourly rate of $10 per hour with no opening bonus. the equations model his salary options. y = 9x + 50 y = 10x

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