Math 2 Lesson: Find the number to be subtracted

### 1.1. Knowledge to remember

### 1.2. Math forms

**Form 1: Find the number to be subtracted**

To find the number to be subtracted, we take the difference plus the minus number.

**Form 2: Fill in the missing numbers in the table**

– Find the difference by subtracting the minus number from the minus number.

– To find the number to be subtracted, we take the difference plus the minus number.

**Form 3: Fill in the missing numbers in the diagram.**

– Observe the given number and operation in the diagram, determine the position of the number to find.

– Do find the missing number and fill in the blank.

### 1.3. Solving Textbook Exercises

**Lesson 1**

Find x:

a) x – 4 = 8

b) x – 9 = 18

c) x – 10 = 25

d) x – 8 = 24

e) x – 7 = 21

g) x – 12 = 36

__Solution method__

To find the number to be subtracted, we take the difference plus the minus number.

__Solution guide__

a) x – 4 = 8

x = 8 + 4

x = 12

b) x – 9 = 18

x = 18 + 9

x = 27

c) x – 10 = 25

x = 25 + 10

x = 35

d) x – 8 = 24

x = 24 + 8

x = 32

e) x – 7 = 21

x = 21+ 7

x = 28

g) x – 12 = 36

x = 36 + 12

x = 48

**Lesson 2**

Write the correct number in the blank:

__Solution method__

– To find the difference, we subtract the minus number from the subtracted number.

– To find the number to be subtracted, we take the difference plus the minus number and then fill in the table.

__Solution guide__

**lesson 3**

Number?

__Solution method__

To find the number to be subtracted, we take the difference plus the minus number.

__Solution guide__

**Lesson 4**

a) Draw line segment AB and line segment CD.

b) Line segment AB and line segment CD intersect at a point. Name that point.

__Solution method__

– Use a ruler and pencil to connect two points A and B; C and D.

– Two lines intersect at a point, marked with a dot and named with a capital letter.

__Solution guide__

Line segment AB and line segment CD intersect at a point O.

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