ptvsever (27*3⁻⁴)²=(3⁻¹)²=1/9
(16*2⁻³)=(2⁴*2⁻³)²=(1/2)²=1/4

6⁻⁴ * 6⁻⁹ / 6⁻¹²  =6⁻¹³ / 6⁻¹² = 1/6
7⁻⁷*7⁻⁸ / 7⁻¹³ = 7⁻¹⁵ / 7⁻¹³ = 7⁻²=1/49

5⁴*49⁻³ / 7⁻⁷*25³ = 5⁴ * 7⁻⁶ / 5⁶ *7⁻⁷ = 5⁻² * 7 = 1/25 * 7 =7/25
81¹² *10⁻⁷ / 10⁻⁵ * 27¹⁷ = 3⁴⁸ *10⁻⁷ / 3⁵¹ * 10⁻⁵ = 3⁻³ * 10⁻² = 1/9 * 1/100=1/900