im not a math fan thats why i didnt get it that easy so ive challenged myself to come up with a simple explanation for the EV of RIT:
for simplicity we are on the river with a pot of $100 and there are only 3 cards left in the deck:
G1, G2 and B. (G=good and B=bad)
so
a) we run it once
G wins ~66% of the time => G=$66
and
B wins ~33% of the time => B=$33
=>
B/G=33/66=1/2
b) we RIT then we have 3 cases:
1) G1 + G2 => $100G
2) G1 + B => $50B + $50G
3) G2 + B => $50B + $50G
so from the total $300 of 3 trials we have G=$200 and B=$100
=>
B/G=100/200=1/2