x+30/100.x= -1,31

(4,5-2x).(\(-1\dfrac{4}{7}\))=\(\dfrac{11}{4}\)

A=1+2+3+4+5+...+99+100

B=\(\dfrac{1}{2}\)+\(\dfrac{1}{6}\)+\(\dfrac{1}{12}\)+\(\dfrac{1}{20}\)+\(\dfrac{1}{30}\)+...+\(\dfrac{1}{9900}\)

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