Soňa Elvíra money

Sonya and Elvira have 20 CZK together, Elvira and Philomena have 15 CZK together, and Sonia and Philomena have 19 CZK together.
How many CZK does Sonya have, how much Elvira, and how much Filomena?

Final Answer:

s =  12
e =  8
f =  7

Step-by-step explanation:

$$\begin{gathered} s+e=20 \\ e+f=15 \\ s+f=19 \\ e+s=20 \\ e+f=15 \\ f+s=19 \\ Row2-Row1\to Row2 \\ f-s=-5 \\ Row3-Row2\to Row3 \\ 2s=24 \\ s=\frac{24}{2}=12 \\ f=-5+s=-5+12=7 \\ e=20-s=20-12=8 \\ e=8 \\ f=7 \\ s=12 \end{gathered}$$

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