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Answer :

AsmaNasrgo

Step-by-step explanation:

3+a=4-b

4+b=7+a

a=1-b

4+b=7+1-b

2b=4

b=2

a=1-2= -1

3-a= 3- -1= 3+1=4

3-a=4

CHERLYNnotCHERRYgo

Answer:

The answer is 4.

Step-by-step explanation:

First, you have to form simultaneous equations :

[tex]3 + a = 4 - b[/tex]

[tex]a + b = 1 - - - (1)[/tex]

[tex]4 + b = 7 + a[/tex]

[tex]a - b = - 3 - - - (2)[/tex]

Next, you have to solve it :

[tex](1) - (2)[/tex]

[tex]a + b - (a - b) = 1 - ( - 3)[/tex]

[tex]2b = 4[/tex]

[tex]b = 2[/tex]

[tex]sub \: \: b \: = 2 \: \: into \: \: (1)[/tex]

[tex]a + 2 = 1[/tex]

[tex]a = 1 - 2[/tex]

[tex]a = - 1[/tex]

Lastly, you have to substitute a-value into the expression :

[tex]3 - a = 3 - ( - 1) = 4[/tex]

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