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1) aflal pe a
(a:5-4):3-260:2=1
2)
100x(6x9-Ax7-4)=100
3)Ax4+(6x7-5x6-72:8)x76=332
4)800:[425-13x(42:4)-89+Ax4)]=10


Răspuns :

1)(a:5-4):3-260:2=1
(a:5-4):3-130=1
(a:5-4):3=1+130
(a:5-4):3=131
a:5-4=131×3
a:5-4=393
a:5=393+4
a:5=397
a=397×5
a=794

2)100×(6×9-a×7-4)=100
100×(54-7a-4)=100
54-7a-4=100:100
54-7a-4=1
-7a=1-54+4
-7a=-53+4
-7a=-49 |:(-7)
a=7

3)a×4+(6×7-5×6-72:8)×76=332
4a+(42-30-9)×76=332
4a+(12-9)×76=332
4a+3×76=332
4a+228=332
4a=332-228
4a=104
a=104:4
a=26

4)800:[425-13×(42:4)-89+a×4)]=10
800:(425-13×21/2-89+4a)=10
800:(425-273/2-89+4a)=10
425-273/2-89+4a=800:10
425-273/2-89+4a=80
4a=80-425+273/2+89 |×2
8a=160-850+273+178
8a=-690+273+178
8a=-417+178
8a=-239
a=-239/8