Birthday

Mother bought 21 desserts on the occasion of Mirka's birthday one tips was 9 CZK and the kremlin cost 12 CZK. For all desserts, she paid 213 CZK. How many kremlins and how many tips mums did buy?

Correct answer:

k =  8
s =  13

Step-by-step explanation:


k+s = 21
9s + 12k = 213

k+s = 21
9·s + 12·k = 213

k+s = 21
12k+9s = 213

Pivot: Row 1 ↔ Row 2
12k+9s = 213
k+s = 21

Row 2 - 1/12 · Row 1 → Row 2
12k+9s = 213
0.25s = 3.25


s = 3.25/0.25 = 13
k = 213-9s/12 = 213-9 · 13/12 = 8

k = 8
s = 13

Our linear equations calculator calculates it.



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