реши уравнение 420-х*5=300;с*9-180=540

420-х×5=300Х×5=420-300Х×5=120Х=120÷5Х=24-----------------420-24×5=300300=300с×9-180=540с×9=540+180с×9=720с=720÷9с=80--------------80×9-180=540540=540