(16m+5m):18=4
21m : 18 = 4
21m = 4*18
21m=72
m=72:21
m=3 9/21 ili 3 3/7
_________________________
(16m+5m):18=4
21m : 18=4
21*3 3/7 : 18 = 4
21*24/7 : 18 = 4
3*24 : 18 = 4
72 : 18 = 4
4 = 4
(17 n-8 n)*13=351
9n * 13 = 351
9n = 351 : 13
9n = 27
n = 27 : 9
n = 3