Here,

i.e.

(∵a=3;d=2;a’=5;d’=3)

∴n(2+n) =7×5×37

∴n²+2n-1295=0

∴(n-35) (n+37) =0

∴ n=35 or n=-37 which is not possible as n is non negative.

So,n=35