48a+25a+7=443; 4(9+7х)+21=393
48а+25а+7=443 48а+25а=443-7 (48+25)а=436 73а=436 а=436:73 а=5,9
48а+25а+7=443; 73а=443-7; 73а=436; а=436:73; а=5,97 4(9+7х)+21=393; 36+28х=393-21; 28х=372-36; 28х=336; х=336:28; х=12