Упростите выражения: a) 0,4n - 0,7m - 0,9n + 0,7m; б) 6c - 8c - 4c + 21 - 13; г) 9/4x - 3/18x - 11/4; д) 0,3m - 2/7 - 3m + 1/7; в) 3/4a + 5/6b - 1/8a - 1/3b; е) 7/4a + 1/4c - 1/7a + 3/4c.

a) 0,4n - 0,7m - 0,9n + 0,7m;

• \(0,4n - 0,9n = -0,5n\)
• \(-0,7m + 0,7m = 0\)

Ответ: \(-0,5n\)

б) 6c - 8c - 4c + 21 - 13;

• \(6c - 8c - 4c = -6c\)
• \(21 - 13 = 8\)

Ответ: \(-6c + 8\)

г) \(\frac{9}{4}x - \frac{3}{18}x - \frac{11}{4}\);

• \(\frac{3}{18} = \frac{1}{6}\)
• \(\frac{9}{4}x - \frac{1}{6}x = \frac{27}{12}x - \frac{2}{12}x = \frac{25}{12}x\)

Ответ: \(\frac{25}{12}x - \frac{11}{4}\)

д) 0,3m - \(\frac{2}{7}\) - 3m + \(\frac{1}{7}\);

• \(0,3m - 3m = -2,7m\)
• \(-\frac{2}{7} + \frac{1}{7} = -\frac{1}{7}\)

Ответ: \(-2,7m - \frac{1}{7}\)

в) \(\frac{3}{4}a + \frac{5}{6}b - \frac{1}{8}a - \frac{1}{3}b\);

• \(\frac{3}{4}a - \frac{1}{8}a = \frac{6}{8}a - \frac{1}{8}a = \frac{5}{8}a\)
• \(\frac{5}{6}b - \frac{1}{3}b = \frac{5}{6}b - \frac{2}{6}b = \frac{3}{6}b = \frac{1}{2}b\)

Ответ: \(\frac{5}{8}a + \frac{1}{2}b\)

е) \(\frac{7}{4}a + \frac{1}{4}c - \frac{1}{7}a + \frac{3}{4}c\).

• \(\frac{7}{4}a - \frac{1}{7}a = \frac{49}{28}a - \frac{4}{28}a = \frac{45}{28}a\)
• \(\frac{1}{4}c + \frac{3}{4}c = \frac{4}{4}c = c\)

Ответ: \(\frac{45}{28}a + c\)