I need help on this question

Which value is not a solution of 8x^3 – 1 = 0

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.

If t17 = 3 (t5) in an arithmetic progression, find t1 in terms of d.