4/3-7/12+9/20-11/30+13/42-15/56+17/72=4/3-(3+4)/(3*4)+(4+5)/(4*5)-(5+6)/(5*6)+(6+7)/(6*7)-(7+8)/(7*8)+(8+9)/(8*9)=4/3-1/4-1/3+1/5+1/4-1/6-1/5+1/7+1/6-1/8-1/7+1/9+1/8=4/3-1/3+1/9=10/9