Answer: 3.1%
====================================================
Work Shown:
P = amount invested (aka principal) = 15,000
r = unknown annual interest rate
t = elapsed time in years = 2
i = simple interest earned = 930
------------------
i = P*r*t ..................... is the simple interest formula
930 = 15000*r*2 .... plug in given values
930 = 15000*2*r
930 = 30000r
30000r = 930
r = 930/30000 ..... divide both sides by 30000
r = 0.031
Multiply that by 100 to convert to a percentage
0.031 ---> 100*0.031 = 3.1%
So r = 0.031 is the same as r = 3.1%