Упростите выражение
15,1c + 0,9(4c-2,8(1,4+0,2))-20c

15.1c+0.9(4c-2.8*1.4-2.8*0.2)-20c=15.1c+0.9(4c-3.92-0.56)-20c=12.1c+0.9*4c-0.9*(-4.48)-20c=12.1c+3.6c-20c-4.032=-1.3c-4.032