(0,6ab-0,5bc+cd)-(-0,5ab+2,5bc-cd)=

(.6ab - .5bc + cd) - ( - .5ab + 2.5bc - cd)    ........distribute the negative across the terms inside the second set of parenthesis

.6ab - .5bc + cd  + .5ab - 2.5bc + cd        .....combine like terms....

1.1ab - 3bc + 2cd