( 16 + 48 ) : 2 - 12 =20
1) 16 + 48 =64
2) 64 : 2=32
3) 32 -12 =20
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(х-25)*6:2 = 42
(х-25)*6 = 42*2
(х-25)*6 = 84
х-25 = 84:6
х-25 = 14
х = 14+25
х = 39
проверим:
(39-25)*6:2=42
42=42
31850-x+69299=13046
x=31850+6299=38149-13046
x=25103