Vacation 35133

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?

Correct 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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