Question

For each diagram, determine whether angles 1 & 2 form a linear pair, heeelp please :(

Answer 1

only (12) has a linear pair

Explanation:

Recall that for two angles to be called a "Linear Pair", they need to satisfy several conditions:

1) The two lines must intersect at a shared point (i.e common vertex)

2) The two angles must be adjacent (i.e immediately next to one another)

3) The two angles must add up to 180 degrees.

In our case,

in (9), the angles are not adjacent and they do not add up to 180 deg, so this is NOT a linear pair

in (10), the angles are not adjacent and they do not add up to 180 deg, so this is NOT a linear pair

in (11), the lines do not intersect at a shared point(they do not have a common vertex). Plus we cannot be 100% sure that they add up to 180 deg. Hence this is not a linear pari

in (12), we can see that the angles satisfy all 3 conditions above. This is a linear pair.