Solve for X

Stars are worth 5$. If Joe has 5$ and Beth has 3 Euros, good for them.
{t}: You get an A+ in target subject if the subject is not violology
{t}: Target subject you control becomes math and target subject an opponent controls becomes violology. Permanently. Aww, too bad.
{3}: Untap this "enchantment artifact land"
If Joe has 3$, how many stars can he buy? round to the nearest life total.