Hamsters and guinea pigs

In the morning, they had five times more hamsters than guinea pigs in the store. After selling 4 guinea pigs and 4 hamsters, they were left with four times as many hamsters as guinea pigs. How many hamsters and guinea pigs did they have together in the shop in the morning?

Final Answer:

x =  -72

Step-by-step explanation:


x=s+m
s=5m
(s-4) = 4(m-4)

x=s+m
s=5·m
(s-4) = 4·(m-4)

m+s-x = 0
5m-s = 0
4m-s = 12

Pivot: Row 1 ↔ Row 2
5m-s = 0
m+s-x = 0
4m-s = 12

Row 2 - 1/5 · Row 1 → Row 2
5m-s = 0
1.2s-x = 0
4m-s = 12

Row 3 - 4/5 · Row 1 → Row 3
5m-s = 0
1.2s-x = 0
-0.2s = 12

Row 3 - -0.2/1.2 · Row 2 → Row 3
5m-s = 0
1.2s-x = 0
-0.167x = 12


x = 12/-0.16666667 = -72
s = 0+x/1.2 = 0-72/1.2 = -60
m = 0+s/5 = 0-60/5 = -12

m = -12
s = -60
x = -72

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