Family

Martin has just as brothers and sisters. But his sister Jana has two times more brothers than sisters.

a) How many children are in this family?
b) How many boys and how many girls are in the family?

Correct answer:

a =  7
b =  4
c =  3

Step-by-step explanation:


a = b+c
b -1 = c
2(c - 1) = b

a = b+c
b -1 = c
2·(c - 1) = b

a-b-c = 0
b-c = 1
b-2c = -2

Row 3 - Row 2 → Row 3
a-b-c = 0
b-c = 1
-c = -3


c = -3/-1 = 3
b = 1+c = 1+3 = 4
a = 0+b+c = 0+4+3 = 7

a = 7
b = 4
c = 3

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