2/3(6,9c-1.1/2d)-4,8(5/8c-2,5d)

2/3 * 6,9с - 2/3 * 1 1/2d - 4,8 * 5/8c + 4,8 * 2,5d =

2/3 * 69/10c - 2/3 * 3/2d - 48/10 * 5/8c + 12d =

23/5c - d - 6/2c + 12d=

4,6c - 3c - d + 12d=

1,6c + 11d.