Ta có: $\widehat{B}-\widehat{C}={{10}^{0}}\Rightarrow \widehat{C}=\widehat{B}-{{10}^{0}}$

Mặt khác trong tam giác ABC ta có:

$\widehat{A}+\widehat{B}+\widehat{C}={{180}^{0}}$

$\Rightarrow \widehat{A}+\widehat{B}+\widehat{B}-{{10}^{0}}={{180}^{0}}$

$\Rightarrow 2\widehat{B}={{180}^{0}}+{{10}^{0}}-\widehat{A}$

$\Rightarrow 2\widehat{B}={{180}^{0}}+{{10}^{0}}-{{70}^{0}}$

$\Rightarrow \widehat{B}={{60}^{0}}$