2/3*(6,9с-1 1/2d)-4 8/10*(5 5/8с-2 5/10а)

2/3 * (6,9с - 1 1/2d) - 4 8/10 * (5 5/8с - 2 5/10а) = 2/3 * (69/10с - 3/2d) - 48/10 * (45/8c - 25/10a) = 46/10c - d - 27c + 12a = 4,6c - d - 27c + 12a = 12a - 22,4c - d