Question

I'm having trouble answering this question

Answer 1

balance= 5000(1+r*t/100)^t -800t where t = no. of years
at t=9, balance becomes 0
0=5000(1+9r/100)^9 -800*9

(1+9r/100)^9=7200/5000=1.44

1+9r/100=1.44^(1/9)=1.04134

9r/100=0.04134

r= 100*0.04134/9 = 0.459 %