Tolong ya no 10 , thanks...

48° + 90° + x = 180°
138° + x = 180°
x = 180°-138°
x = 42°

*semoga membantu. sukses selalu ^_^

<ABC = <ABE + <EBD + <CBD
180 = 48 + 90 + <CBD
180 = 138 + <CBD
<CBD = 180 - 138
<CBD = 42