Write the subtraction as an addition: (-)

Remember that when you subtract a negative number, you are really just adding the number. This is represented as:

Thus, we can simplify

,

as

Our answer is -27 + 27.

< coa = 150 ( given)

as ba and bc are tangents

so oc and oa is perpendicular to cb and ab respectively because in circle normal passes through centre

so in quadrilateral oabc

< coa + < oab + < ocb + < abc = 360

150 +90+90 + < abc = 360

330 + < abc = 360

< abc = 360 -330 = 30

so < abc = 30

⭐dhruv⭐