Question

∆ODC~∆OBA BOC=125° and CDO=70° find angle (DOC DCO and OAB)..

Answer 1

angle DOC + angle BOC = 180(linear pair )
DOC = 180-125
angle DOC = 55
DOC + DCO +ODC = 180(sum of all angle )
angle DCO = 180-125
DCO = 55
Angle OAB = OCD (Alternate an.)
OAB = 55.

Answer 2

$\red{\color{white}{\fcolorbox{cyan}{black}{Answer:-}}}$

$\angle DOC+ \angle BOC=180\degree\\ \angle DOC = 180 \degree - 125\degree \\ \red{\angle DOC = 55\degree} \: \: \: ~~ \: \: (linear \: pair) \\ \\ \angle DCO =180 \degree - (70\degree + 55\degree) \\ \angle DCO =180\degree - 125\degree \\ \red{\angle DCO =55\degree} \ \\ \\ \ Since, \: \triangle ODC \sim \: \triangle OBA \\ \red{\angle OBA = \angle DCO = 55 \degree}$