1 000-[5+2×(100+y×4)-124:4]=754
1 000-[5+2×(100+y×4)- 31]=754
[5+2×(100+y×4)- 31]= 1 000- 754
5+2×(100+y×4)- 31 = 246
5+2×(100+y×4) = 246+ 31
5+2×(100+y×4) = 277
2×(100+y×4) = 277- 5
2×(100+y×4) = 272
(100+y×4) = 272: 2
100+y×4 = 136
y×4 = 136- 100
y×4 = 36
y = 36: 4
y = 9
