I = prt calculates the amount of simple interest. I represents the interest, p the principle, r and the percentage rate and t the amount of time.
We know that t = 6 years, p = 7000, and I = 1890.
So 1890 = 7000r6
1890 = 42000r
Divide both sides by 42000
1890 / 42000 = 42000r / 42000
r = 0.045.
So the percentage rate is 4.5%
Hope this helps! :D