Question

42240:(140*х-860)=352

Answer 1

140X - 860 = 42240 : 352 = 120 
    140X = 120 + 860 = 980 
    X = 980 : 140 = 7

Answer 2

42240:(140*х-860)=352
140*х-860=42240:352
140*х-860=120
140*х=120+860
140*х=980
х=980:140
х=7
проверка
42240:(140*7-860)=352
42240:(980-860)=352
42240:120=352
352=352