Question

5/7 (2,8с- 21/5d) - 2,4(5/6c - 1,5d)

Answer 1

Раскроем скобки:
$frac{5*28}{7*10}c - frac{5*21}{7*5}d - frac{24*5}{10*6}c + frac{24*15}{10*10} d$
Упростим:
$2 c - 3d - 2c + 3.6 d = 0.6 d$