ANSWER for Algebra Practise- See how smart you are

Answer:

First number = A
Second number = B
Third number = C
Fourth Number = D
Fifth Number = E

Put up the equations according to the clues:

Equation 1: C + E = 14
Equation 2: D = B + 1
Equation 3: A = 2B – 1
Equation 4: B + C = 10
Equation 5: A + B + C + D + E = 30

Put Equation 4 into Equation 5
A + (10) + D + E = 30
A + D + E = 20

Put in Equation 1,2 and 3
(2B – 1) + (B + 1) + (14 – C) = 20
2B – 1 + B + 1 + 14 – C = 20
3B – C = 6

From equation 4, we know C = 10 – B
Hence, 3B – (10 – B) = 6
3B – 10 + B = 6
4B = 16
B = 4

A = 2B – 1 = 2(4) – 1
A = 7

B + C = 10
C = 10 – 4
C = 6

D = B + 1 = 4 + 1
D = 5

C + E = 14
E = 14 – (6)
E = 8

Hence, the code to enter to the building is 74658

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Algebra Practise- See how smart you are