=1+150/(3*5)+150/(5*7)+150/(7*9)+150/(9*11)+150/(11*13)
=1+75*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13)
=1+25-75/13
=263/13
=1+150/(3*5)+150/(5*7)+150/(7*9)+150/(9*11)+150/(11*13)
=1+75*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13)
=1+25-75/13
=263/13