(420+х)+300=1000
160+(х+250=8000

(420+х)+300=1000

420+х+300=1000

х=1000-420-300

х=280

Пошаговое объяснение:

160+(х+250)=8000

160+х+250=8000

х=8000 - 160 -250

х=7590

(420+х)+300=1000

420 + x = 1000 - 300

420 + x = 700

x = 700 - 420

x = 280

160+(х+250)=8000

x + 250 = 8000 - 160

x + 250 = 7840

x = 7840 - 250

x= 7590