Lucka candy count

Ten different packages contain 1 to 10 candies respectively. Each child took two packages. They received the following number of candies:
Annie: 5
Suzy: 7
Katie: 9
Monica: 15
How many candies does Lucy have?

Final Answer:

L =  19

Step-by-step explanation:

$$\begin{gathered} s=1+2+3+4+5+6+7+8+9+10=55 \\ A=5 \\ Z=7 \\ K=9 \\ M=15 \\ x=A+Z+K+M=5+7+9+15=36 \\ L=s-x=55-36=19 \end{gathered}$$

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