$\dfrac{13}{42}$ `+` `( -` $\dfrac{5}{18}$ `)` `-` $\dfrac{11}{21}$ `-` `( - `$\dfrac{4}{14}$ `)`
`=` `(` $\dfrac{13}{42}$ `-` $\dfrac{11}{21}$ `+` $\dfrac{4}{14}$ `)` `-` $\dfrac{5}{18}$
`=` $\dfrac{13 - ( 11 . 2 )+ ( 4 . 3 )}{42}$ `-` $\dfrac{5}{18}$
`=` $\dfrac{1}{14}$ `-` $\dfrac{5}{18}$
`=` $\dfrac{9 - 35}{126}$ `=` $\dfrac{-26}{126}$ `=` $\dfrac{13}{63}$