For each problem, use the inscribed angle theorem.
19.
[tex]45^\circ=\dfrac12m\widehat{QR}\implies m\widehat{QR}=90^\circ[/tex]
20.
[tex]95^\circ=\dfrac12m\widehat{ABC}\implies m\widehat{ABC}=190^\circ[/tex]
21.
[tex]49^\circ=\dfrac12m\widehat{LR}\implies m\widehat{LR}=98^\circ[/tex]
LN is a diameter, so arc LN has measure 180º, and so
[tex]m\widehat{LR}+m\widehat{RN}=m\widehat{LN}=180^\circ\implies m\widehat{RN}=82^\circ[/tex]
