5/16 : (9 - 6 1/8 · 1 2/7) = 5/18
1) 6 1/8 · 1 2/7 = 49/8 · 9/7 = (7·9)/(8·1) = 63/8 = 7 7/8
2) 9 - 7 7/8 = 8 8/8 - 7 7/8 = 1 1/8
3) 5/16 : 1 1/8 = 5/16 : 9/8 = 5/16 · 8/9 = (5·1)/(2·9) = 5/18
- - - - - - - - - - - - - - -
(3/4)х - 12,5 = (9/8)х - 1/8
(9/8)х - (3/4)х = 1/8 - 12,5
1,125х - 0,75х = 0,125 - 12,5
0,375х = - 12,375
х = - 12,375 : 0,375
х = - 33
Проверка:
-(3·33)/4 - 12,5 = -(9·33)/8 - 0,125
-24,75 - 12,5 = -37,125 - 0,125
-37,25 = -37,25