300–x*5=210 (300–x)*5=210 (150–20): x=65 (x+4)*7=350 (300–18)*x=1410 5*x–600=900

Х*5 = 300 - 210 = 90
х=90*5 = 18
300-х = 210:5= 42
х=300-42=258
130:х=65
х=130:65=2
х+4=350:7=50
х=50-4=46
282*х=1410
х=1410:282=5
5*х=600+900=1500
х=1500:5=300