How to add and subtract fractions with different denominators?

you times the denominators together and what you do to the bottom you have to do it on top. then you add or subtract the numerators.

sorry, i don't know i just need points, i'm new here. chao

< 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⭐