Please help I would really Appreciate it so much

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

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are:

Ricky takes out a $31,800 student loan to pay his expenses while he is in college. after graduation, he will begin making payments of $190.66 per month for the next 30 years to pay off the loan. how much more will ricky end up paying for the loan than the original value of $31,800? ricky will end up paying $ more than he borrowed to pay off the loan.