(х+51)*309=16686  9435/(77-x)=555 

(х+51)*309=16686 х+51= 16686:309 х+51= 54 х= 54-51 х=3 _______ (3+51)*309=16686 16686=16686 9435:(77-х)=555 77-х=9435:555 77-х=17 х=77-17 х=60 ________ 9435:(77-60)=555 555=555