Find the angle that makes them supplementary. ∠3=50 so ∠4=
∠5=70 so ∠6=
∠7=140 so ∠8=
∠9=90 so ∠10=
∠11=115 so ∠12=

Mathematics NCERT Grade 7, Chapter 5: Lines and Angles is all about different lines, line segments, and angles.

A line segment has two end points.

A ray has only one end point (its vertex).

A line has no end points on either side.  

This chapter throws light on topics such as related angles, pair of lines. The chapter deals with different types of angles and lines. The types of angles discussed in this chapter are as follows:

Pairs of Angles          Condition

Two complementary anglesMeasures add up to 90°

Two supplementary anglesMeasures add up to 180°

Two adjacent anglesHave a common vertex and a common arm but no common interior

Linear pairAdjacent and supplementary

A linear pair is a pair of adjacent angles whose non-common sides are opposite rays.

All the types are discussed in detail and are supplemented with examples and short questions.  

Under the topic pair of lines, various sub-sections are discussed namely:

Intersecting lines

Transversal  

Angles made by a transversal

When two lines intersect (looking like the letter X) we have two pairs of opposite angles. They are called vertically opposite angles. They are equal in measure.

A transversal is a line that intersects two or more lines at distinct points.

Six angles discussed in this section:

1. Interior angles

2. Exterior angles

3. Pairs of Corresponding angles

4. Pairs of Alternate interior angles

5. Pairs of Alternate exterior angles

6. Pairs of interior angles on the same side of the transversal

Transversal of parallel lines

answer: 180

step-by-step explanation:

12-2=10

20-2=18

10x18=180

step-by-step explanation: