Cindy has $60 in her bank account while Eric has $400 in his bank account. Cindy deposits
$5 into her bank account every day while Eric withdraws $10 from his bank account every
day. How many days, d, will it take for Cindy and Eric to have the same amount of money
in their bank accounts?
60 - 10d = 400 +5d
60 - 5d = 400 +10d
60 - 5d = 400 - 10d
60 + 5d = 400 - 10d