Answer:
2 %
Step-by-step explanation:
Money borrowed, Principal, P = $ 700
time of investment, T = 3 years
Total interest paid, Simple interest, S.I = $ 42
Let the rate of interest is R.
Use the formula for simple interest.

By substituting the values

4200 = 2100 R
R = 2 %
Thus, the rate of interest is 2%.