Answer:
[tex](45x) \degree = (25x)\degree + (57 + x)\degree \\ \{{ \sf{external \: angle \: is \: equal \: to \: interior \: angle \: sum \}}} \\ 45x - 25x - x = 57 \\ 19x = 57 \\ { \underline{ \underline{ \: \: x = 3 \: \: \: }}}[/tex]
