Bonjour,
1) 5/12 = 35/ n
(5/12) /35 = n
5/12 * 1/35 = n
5/420 =n
1/84 =n
2) n/ 52 = 180/ 120
n= (180*52)/120
n=9 360/120 = 936/12 = 78
3) 18/n = 21/28
n = (21/28)/18
n = 21/28 * 1/18
n= 21/504 = 7/168= 1/24
4) n/4 = 24/6
n= 24/6 * 4
n= 96/6 =16
5) 10/16 = n/56
n= 10/16 * 56
n= 560/16
n= 35
