раскройте скобки 10x+(8x-(6x+4)
10x+(8x-(6x+4))=10х+(8х-6х-4)=10х+8х-6х-4=(10х+8х-6х)-4=12х-4
10x+(8x-(6x+4))=10x+8x-(6x+4)=18x-6x-4=12x-4