What would be the mass ratio of Pb-208/Th-232 in a meteorite that is approximately 4.5 × 10^9 years old? The half-life of Th-232 is 1.39 x 10^10 years

i'm used t= 3.32 t(1/2) logNo/N but the result is not correct !?

4.5/13.9 = .323 not 3.32

x = Xo (1/2)^n
log (x/Xo) = n log .5

= .323(-.301) = -.09723
x/Xo = 10^-.09723 = .799