i havent been in school in a long time, but the questions are fairly basic. is this an entry-level finance class? simply think in terms of yield and discounting to NPV. on an HP-12C you have NPV, FV, i (interest) and n (periods). in the first one you are calculating yields on 2 investments. just do it. then, you discount the cashflows and reversions back at 6% and then 12%. straight forward. by the way, think what would happen if you were buying the investments back at YOUR required yield!
the next one was the $900 security. first, just sit back and think - you are getting $50 annual cashflow on $900, or 5.56% and the reversion is $150 more than the $900 (PV) or 16.67% (ignore compounding for now - the period is rather short). so you can probably guess that given the 5.56% cashflow and 5.5% (+/-) annual appreciation, you can see that the security (assuming similar risk profile) is probably a superior investment to the 8% annual yield on the savings account.
the last one is just calcualting interest with a "twist" on the amortization.
again, im an old fart (47 yrs) that is a long way out of college, but i can tell you these types of questions are excellent if you want to buy mortgage notes, invest in real estate, etc. apply yourself now, and the rest will be easier. my 10 yo and 13 yo can calculate basic payments, NPV, FV and yield. most people cant come close to working a financial calculator. dont give up!
good luck,
scott
edit: i just read your angry response. just set up the problem into initial investment (-NPV)/cashflow-payments/FV; and solve for i (interest/yield). BTW, i never took a finance class, but i think my approach is right. believe me, you can really use this stuff.
here's real world: stupid realtor carries their $15,000 commission as a 2nd Turst Deed at 10% interest only, monthly payments. then realtor cant make payments on the benz or leased, oceanfront condo; so he is forced to sell you the note for $12,000 (a day or so later). your yield approaches 19% (NPV = -$12,000/FV = $15,000/PMT = $125/n = 36/solve for i). i = 18.95%.
now, you go to the homeowner and say: if you pay the note off in 2 years i will cut the interest to 9%(i only/monthly). solve for yield. NPV = -$12,000/FV = $15,000/PMT = $112.50/n = 24/solve for i. i = 21.56%. pretty good yield on 2-year investment that is collateralized by real estate! certainly better than originating the note!