Family luggage weight

The family is going on vacation. Everyone has their luggage. Together the luggage weighs 21kg. The mother's luggage weighs two times more than the father's and the son's 4 kilograms less than the mother's. How much does luggage weigh?

Final Answer:

m =  10
s =  6
t =  5

Step-by-step explanation:


m+t+s=21
m=2t
s = m-4

m+t+s=21
m=2·t
s = m-4

m+s+t = 21
m-2t = 0
m-s = 4

Row 2 - Row 1 → Row 2
m+s+t = 21
-s-3t = -21
m-s = 4

Row 3 - Row 1 → Row 3
m+s+t = 21
-s-3t = -21
-2s-t = -17

Pivot: Row 2 ↔ Row 3
m+s+t = 21
-2s-t = -17
-s-3t = -21

Row 3 - -1/-2 · Row 2 → Row 3
m+s+t = 21
-2s-t = -17
-2.5t = -12.5


t = -12.5/-2.5 = 5
s = -17+t/-2 = -17+5/-2 = 6
m = 21-s-t = 21-6-5 = 10

m = 10
s = 6
t = 5

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