Subtract 82442

I think of three numbers. When I add them, I get 15. When I subtract the third number from the sum of the first two numbers, I get 10. When I subtract the second number from the sum of the first and third numbers, I get 8. What number do I think?

Correct answer:

a =  9
b =  3.5
c =  2.5

Step-by-step explanation:


a+b+c=15
a+b-c=10
a+c-b=8

a+b+c = 15
a+b-c = 10
a-b+c = 8

Row 2 - Row 1 → Row 2
a+b+c = 15
-2c = -5
a-b+c = 8

Row 3 - Row 1 → Row 3
a+b+c = 15
-2c = -5
-2b = -7

Pivot: Row 2 ↔ Row 3
a+b+c = 15
-2b = -7
-2c = -5


c = -5/-2 = 2.5
b = -7/-2 = 3.5
a = 15-b-c = 15-3.5-2.5 = 9

a = 9
b = 7/2 = 3.5
c = 5/2 = 2.5

Our linear equations calculator calculates it.



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