1а)125000000=1,25×10⁸
б)87000000000=8,7×10¹⁰
с)790000000000=7,9×10¹¹
2а)0,000000012=1,2×10-⁸
б)0,0000000087=8,7×10-⁹
с)0,000189=1,89×10-⁵