`15/34+7/21+9/34-1 15/17+2/3`
`=(15/34+9/34)+(7/21+2/3)-32/17`
`=12/17+1-32/17`
`=(12/17-32/17)+1`
`=-20/17+1`
`=-3/17`
\(\dfrac{15}{34}+\dfrac{7}{21}+\dfrac{9}{34}-1\dfrac{15}{17}+\dfrac{2}{3}\)
\(=\left(\dfrac{15}{34}+\dfrac{9}{34}-\dfrac{32}{17}\right)+\left(\dfrac{1}{3}+\dfrac{2}{3}\right)\)
\(=-\dfrac{25}{17}+1=-\dfrac{8}{17}\)