Robetinoask
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529. Aflaţi numărul a, dacă:
a) 310- a * (100 – 30 x 3) = 280;
b) 64 – 120: (30 2:10) - a = 40;
c) 406 - 4* [a (30 - 20:5:4)] = 58;
d) (21 - (648: 24 + a): 7] 3 + 55=100;
e) (1 860:3+ (a + 164): 2 + 7]: 8 = 100​

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Andreea16087ask

A 310-a×(100-30×3)=280
310-a×(100-90)=280
310-a×10=280
10a=310-280
10a=30
a=30÷10
a=3
B 64-120:(30×2:10)-a=40
64-120÷(60÷10)-a=40
64-120÷6-a=40
64-20-a=40
44-a=40
a=44-40
a=4
C 406-4×[a×(30-20:5:4)]=58
406-4×[a×(30-1)]=58
406-4×(a×29)=58
406-4×a×29=58
406-116a=58
116a=406-58
116a=348
a=348÷116
a=3
D [21-(648÷24+a)÷7]×3+55=100
[21-(27+a)÷7]×3=100-55
[21-(27+a)÷7]×3=45
21-(27+a)÷7=45÷3
21-(27+a)÷7=15
(27+a)÷7= 21-15
(27+a)÷7=6
27+a=6×7
27+a=42
a=42-27
a=15
E [1860÷3+(a+164)÷2+7]÷8=100
[620+(a+164)÷2+7]=100×8
620+(a+164)÷2+7=800
620+(a+164)÷2=800-7
620+(a+164)÷2=793
(a+164)÷2=793-620
(a+164)÷2=173
a+164=173×2
a+164=346
a=346-164
a=182
Succes!

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