I=Interest

P=Principal amount=2600

r=rate of interest=20/3%

t=time in years

I=Prt

I=2600*[(20/3*100)]*1=173.33.............(for't'=1year)............(I=decimal figure)

I=2600*[(20/3*100)]*2=346.67.............(for 't'=2 year.s........(I=decimal figure)

I=2600*[(20/3*100)]*3=520...................(for 't'=3years........(I=exact number)

so least no of years=3

ans is 3 years