Refractive index of material A = speed of light in vacuum/speed of light in material A
According to question, speed of light in material A = 1.45*10^8 m/s and speed of light in vacuum = 3*10^8 m/s.
Hence, refractive index of material A = 3*10^8/1.45*10^8 = 3/1.45 = 2.07
Refractive index of material A/refractive index of material B = 1.34.
or, 2.07/refractive index of material B = 1.34
or, refractive index of material B = 2.07/1.34
therefore, refractive index of material B = 1.55.
Hence we know that speed of light in material B = speed of light in vacuum / refractive index of material B = 3*10^8 / 1.55 = 1.94*10^8 m/s