Interest: Subtract the principal from the maturity value:

I= $270
Principal: Value of the loan
P=$9,000
time: Turn the 3-months into years:

t=0.25 years
Having the data for P, I and t, use the formula (I=Prt) to solve r:

Interest rate: r=0.12
Multiply the interest rate by 100 to write it as a percent:

Annual simple interest rate: 12%