Question

 x– 1/10 − 1/15 − 1/21 − ⋯ − 1/120 = 3/8

Answer 1

=>x-(2/20+2/30+...+2/240)=3/8

=>x-2(1/4-1/5+1/5-1/6+...+1/15-1/16)=3/8

=>x-2*3/16=3/8

=>x=3/8+3/8=3/4