Bonsoir,
2/3 +1/2 = 4/6 + 3/6 = 7/6
17/9 -1/3 = 17/9 -3/9 = 14/9
(7/6) /( 14/9 )
=7/6 * 9/14
= 63/84
=21/28
=3/4
(486*10^-7)/ (18*10^-2)
= (486 * 10^-5) / 18
= 27*10^-5