$5\widehat{M}=3\widehat{N}\Rightarrow \widehat{M}=\frac{3\widehat{N}}{5}$

Thay vào $7\widehat{M}-4\widehat{N}={{15}^{0}}$ ta được:

$7.\frac{3\widehat{N}}{5}-4\widehat{N}={{15}^{0}}$

$\frac{1}{5}\widehat{N}={{15}^{0}}\Rightarrow \widehat{N}={{75}^{0}}\Rightarrow \widehat{M}={{45}^{0}}$

Trong tam giác MNP có:

      $\widehat{M}+\widehat{N}+\widehat{P}={{180}^{0}}$ thay số ta được:

      45$^{0}+{{75}^{0}}+\widehat{P}={{180}^{0}}$

      $\widehat{P}={{60}^{0}}$