12 is decided by 2 and 3 so it’s not prime
Mikhail has $3.000 of his $12.000 invested in cd's, which is 3.000/12.000 = 1/4 of his total savings portofolio. Ivan too has 1/4 of his total savings portofolio invested in cd's, which is $2.000. So Ivan's total savings portofolio is 4 x $2.000 = $8.000