Odpowiedź:
a) 12x - 3y + 10 - 20y - 4x - 9+ 6x - 13 + 8y =12x-4x+6x-3y-20y+8y+10-9-13=14x-15y-12
b) - 4a + 16b - 7 + 2a + 3b - 3 + 14a - 10b + 6 = 12a-9b-4
c)-(- 3a - 4b + 7) - (12b-9a - 10b + 15) =-3a-4b+7-12b+9a+10b-15=12a-6b-22
d) - 8+ [-2a - (-3a + 2b - 4) - (6b+12a + 8 - 3b)] = -8+(-2a+3a-2b+4-6b-12a-8+3b)= -8-2a+3a-2b+4-6b-12a-8+3b= -4-13a-5b