Answer:
5%
Step-by-step explanation:
The equation for simple interest rate is as follows: 
A = P(1+rt)
A = final amount 
P = initial principal amount
r = annual interest rate
t = time (in years) 
So, we need to plug everything in and solve for r: 
The final amount is equal to $875 plus the interest of $131.50.
A = 875 + 131.50 = 1006.50
Now, plug everything in: 
1006.50 = 875( 1 + r(3))
Solve: 
1 + 3r = 1.15028571                            Divide 1006.50 by 875
3r = 0.15028571                                Subtract 1 from 1.15028571
r = 0.050                                           Divide by 3
The simple interest rate would be 5%. I converted the r to a percent by multiplying 0.050 by 100. 
I hope this helps!! Ask questions if you need!!