求未知數2條 - 10點

第一題:

1A + 2B + 1C = 20
2A + 2B = 22
2A + 1B + 1C = 21

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2A + 2B = 22
A + B = 22/2
A = 11-B
1A + 2B + 1C = 20
(11-B) + 2B + 1 C = 20
11 + 1B + 1C = 20
C = 20-11- 1B
C = 9-1B
2A + 1B + 1C = 20
2 (11-B) + 1B + 1(9-1B) = 21
22 - 2B + 1B + 9 – 1B = 21
31 – 2B = 21
31 - 21 = 2B
10 / 2 = B
B = 5
2A + 2B = 22
2A + 2(5) = 22
2A+ 10 = 22
2A = 22-10
A = 12 / 2
A = 6
1A + 2B + 1C = 20
1(6) + 2(5) + 1C = 20
6 + 10 + 1C = 20
C = 20-10-6
C = 4

A = 6, B = 5, C = 4



第二題:

2A + 2B = 30
1A + 2B + 1C = 26
2A + 1B + 1C = 33

2A + 2B = 30
2 (A+B) = 30
1A + 1B = 30/2
A = 15 – 1B
1A + 2B + 1C = 26
1(15-B) + 2B + 1C =26
15 – 1B + 2B + 1C = 26
15 + 1B + 1C = 26
1C = 26-15-1B
1C = 11-1B
2A + 1B + 1C = 33
2(15-1B) + 1B + 1(11-1B) = 33
30 – 2B + 1B + 11 – 1B = 33
41 – 2B = 33
41 – 33 = 2B
8 = 2B
B = 4
2A + 2B = 30
2A +2 (4) = 30
2 A+ 8 = 30
2A = 30-8
A = 22 /2
A = 11
1A + 2B + 1C = 26
1(11) + 2(4) +1C = 26
11+8+1C=26
19 + 1C = 26
C = 26-19
C=7

A = 11, B = 4 , C = 7

第一題:::
A=6
B=5
C=4

第二題:::
A=11
B=4
C=7