12. \( x + (x + 1) + (x + 2) + \ldots + (x + 30) = 1240 \) 13. \( 2 + 4 + 6 + 8 + \ldots + 2x = 210 \) 14. \( 5^{1} \cdot 5^{x-1} \cdot 5^{x+2} = 1000 \cdot 2^{18} \)

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12. \( x + (x + 1) + (x + 2) + \ldots + (x + 30) = 1240 \)

13. \( 2 + 4 + 6 + 8 + \ldots + 2x = 210 \)

14. \( 5^{1} \cdot 5^{x-1} \cdot 5^{x+2} = 1000 \cdot 2^{18} \)