500 - 400 ÷ ( x + 43 ) = 495
400 ÷ ( x + 43 ) = 500 - 495
400 ÷ ( x + 43 ) = 5
x + 43 = 400 ÷ 5
x + 43 = 80
x = 80 - 43
x = 37
проверка
500 - 400 ÷ ( 37 + 43 ) = 495
495 = 495
