как решить (200-x)-98=75                             (300+x)+200=800                                                            

(200-x)-98=75    

200-x= 75+98

200-х=173

-х=173-200

х=27

(200-х)-98=75

200-х=75+98

200-х=173

х=200-173

х=27         проверка  

               (200-27)-98=75

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(300+х)+200=800

300+х=800-200

300+х=600

х=600-300   х=300