You can easily calculate how much you have borrowed (3867.35 + 3794.20 + 9584.80 = $17246.35), but it is important to note that this is not how much you owe.
How much you owe is the number of remaining payments, multiplied by the minimum payment amount ((38 * 145.59) + (38 * 134.62) + (30 * 357.93) = $21385.88).
The difference between these two numbers is how much interest you're paying:
$21,385.88 - $17,246.35 = $4,139.53
This is the only number that you can change- one way or another you're going to pay off the full amount borrowed (principleprincipal), but you can reduce or even eliminate the interest ($4139.53!) by paying extra.
While it might be tempting to pay off the larger principleprincipal amount first (reducing 9584.80 to only 584.80!), this will only reduce your interest owed to 3044.34 (you saved 1095.19 in interest and your total amount owed is now $11,290.69).
On the other hand if you pay off the two smaller (but higher interest) loans first- you save around 70% of the interest owed (now a total of $864.88 in interest). However, the total amount you will have left to pay back under this scenario drops to $9111.23, which is $2179.46 less than the other scenario!!
The reason for this difference is subtle, but still intuitive -- the first loan (3867.35 @ 23.55%) ends up accounting for a whopping 40.5% of the total interest paid! The second loan isn't much better, accounting for 31.2% of the total interest. Thus paying off those loans all at once will result in saving over 70% of the variable portion of your debt (interest). While none of these figures account for snowballing the payments, the time to being debt-free is still shorter under the second scenario (14 months) than the first (15 months)!
