Question

find the amount and the compounded intrest on 12800 for one year at 7.5% per annum compounded semi annually

Answer 1

r= 7.5% per annum
i.e 3.75% per semi annually
number of semi annuals=2
A=12800(1+3.75/100)^2=12800(103.75/100)^2
i leave the calculation to you.