Brothers and sisters

Lenka has as many brothers as sisters. Her brothers have twice as many sisters as brothers. How many brothers and sisters are in the family?

Correct answer:

b =  3
s =  4

Step-by-step explanation:


b=s-1; 2(b-1)=s

b=s-1
2·(b-1)=s

b-s = -1
2b-s = 2

Pivot: Row 1 ↔ Row 2
2b-s = 2
b-s = -1

Row 2 - 1/2 · Row 1 → Row 2
2b-s = 2
-0.5s = -2


s = -2/-0.5 = 4
b = 2+s/2 = 2+4/2 = 3

b = 3
s = 4

Our linear equations calculator calculates it.



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