Combined 81039

Katka has k marbles, Petra has 20 more marbles than Katka, and Lenka has 30 marbles less than Petra and Katka combined. How many marbles do they all have in total?

Correct answer:

x = 4k+10

Step-by-step explanation:

$$\begin{gathered} p=20+k \\ l=p+k-30=20+k+k-30=2k-10 \\ x=p+l+k \\ x=20+k+(p+k-30)+k \\ x=20+k+20+k+k-30+k \\ x=4k+10 \end{gathered}$$

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