1/1.2.x+1/2.3.x+...1/9.10 = 18/5
=2-1/1.2.x+3-2/2.3.x+...10-9/9.10 = 18/5
=2/1.2.x - 1/1.2.x + 3/2.3.x - 2/2.3.x +... 10/9.10 - 9/9.10 = 18/5
=1x - 1/2x + 1/2x - 1/3x + ... 1/9 - 1/10 = 18/5
= 1x - 1/10 = 18/5
1x = 18/5 + 1/10
1x = 37/10
x = 37/10
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