Matt borrowed R1800 at 8,5% simple interest yearly. What amount does he need to repay after 9 months

The first step is to calculate the interest for 9 months:

Interest = Principal x Rate x Time
Where:
Principal = R1800
Rate = 8.5% or 0.085 (decimal form)
Time = 9/12 years (since 9 months is equivalent to 9/12 or 0.75 years)

Interest = 1800 x 0.085 x 0.75
Interest = R114.75

Next, we add the interest to the principal to find the total amount to be repaid:
Total = Principal + Interest
Total = R1800 + R114.75
Total = R1914.75

Therefore, Matt needs to repay R1914.75 after 9 months, which includes the original loan amount of R1800 plus interest of R114.75.