Ответ:

m = 175/41

Объяснение:

2/5+3/7=14/35+15/35=29/35=58/70

5/m = 140/70 - 58/70 = 82/70

410/82m = 410/350

82m = 350

41m = 175

[tex]\displaystyle\bf\\1)\\\\\frac{2}{5} +\frac{3}{7} =\frac{2\cdot 7+3\cdot 5}{35} =\frac{14+15}{35} =\frac{29}{35} \\\\\\2)\\\\\frac{29}{35} +\frac{5}{m} =2\\\\\\\frac{5}{m} =2-\frac{29}{35} \\\\\\\frac{5}{m}=\frac{41}{35} \\\\\\m=\frac{5\cdot 35}{41} =4\frac{11}{41}[/tex]