Hello,

So let us suppose,

r1= initial radius

r2=final radius

r2=r1+125%r1=9/4r1

t1=initial duration of 1 year

t2=final duration of 1 year

by Kepler's law we know that t^2 is directly proportional to r^3

therefore

(t2/t1)^2=(r2/r1)^3

t2/t1=(r2/r1)^(3/2)

t2=t1*(9/4r1/r1)^(3/2)

t2=t1*(3/2)^3

t2=365*27/8

this will be the duration of 1 year if the distance of earth and sun increases by 125%.

I hope this helps.

All the best!