1- 500 principal earning 4% compounded quarterly, after 6 year. a - 1.281.65 b - 634.87 c - 709.26 d - 632.66 2 - 3500 deposit earning 6.75% compounded monthly, after 6 months. a - 3,619.80 b - 3,743.70 c - 3,748.22 d - 4,860.36

You'll have $634.87 after 6 years at 4% compounded quarterly, thus B:
You'll have $3,619.80 after 6 months at 6.75% compounded monthly, thus A:

Formulas where n = 1 (compounded once per period or unit t)
1.  Calculate Accrued Amount (Principal + Interest) A = P(1 + r)^t
2. Calculate Principal Amount, solve for P.  P = A / (1 + r)^t
4. Calculate the rate of interest in decimal, solve for r. r = (A/P)1/(^t - 1)
5. Calculate rate of interest in percent. ...Calculate time, solve for t.