The number of obtuse angles in Fig. 2.9 is

Obtuse angles are the angles which are greater than 90° and less than 180°.

so here individually none of them is an obtuse angle.

if we combine 20° and 45° still it is not and obtuse angle.

but, if combine 20° + 45° + 65°

then it is an obtuse angle.

also 20° + 45° + 65° + 30° is not an obtuse angle since its equal to 180°.

Similarly, 65 + 30 and 45 + 65 + 30 are also obtuse.

and 45° + 65° is also obtuse.

∴ 4 angles are obtuse