1) x/72 - 13/72 = 29/72
Х:72=29/72+13/72
Х=42/72*72/1
Х=42
2) (29/42 - a) - 13/42 = 11/42
29/42-а=11/42+13/42
а=29/42-24/42
а=5/42
3) 15/17 - (b - 3/17) = 6/17
-b+3/17=6/17-15/17
-b=-9/17-3/17
b=12/17
4) 29/43 - (m + 13/43) = 5/43
-m-13/43=5/43-29/43
-m=-24/43+13/43
m=11/43