ADDITION AND SUBTRACTION EQUATIONS

About "Addition and subtraction equations"

Addition and subtraction equations are the equations which contain addition or subtraction. 

For example, 

x + 5  =  7

y - 3  =  4

Let us see, how to solve equations which contain addition or subtraction. 

Solving addition and subtraction equations - Examples

Example 1 :

Solve for x :  x + 7  =  8

Solution :

x + 7  =  8

Since we are trying to solve for "x", we have to get rid of 7 which is added to "x".

To get rid of 7, we have to take -7 on both sides. 

aaaaaaaaaaaaaaaaaaaaaaax + 7  =  8 aaaaaaaaaaaaaaaaaaaaaaaaa- 7aa- 7 aaaaaaaaaaaaaaaaaaaaaa------------- aaaaaaaaaaaaaaaaaaaaaaax        =  1 aaaaaaaaaaaaaaaaaaaaaa-------------

Hence, the value of "x" is 1.

Example 2 :

Solve for y :  y - 3  =  2

Solution :

y - 3  =  2

Since we are trying to solve for "y", we have to get rid of 3 which is subtracted from "y".

To get rid of 3, we have to take +3 on both sides. 

aaaaaaaaaaaaaaaaaaaaaay - 3  =  2                 aaaaaaaaaaaaaaaaaaaaaaaa + 3       + 3                                 aaaaaaaaaaaaaaaaaaaaa-----------------                               aaaaaaaaaaaaaaaaaaaaaay            =   5                                 aaaaaaaaaaaaaaaaaaaaa-----------------

Hence, the value of "y" is 5.

Example 3 :

When 7 is added to a number, we get 25. Find the number. 

Solution : 

Let "x' be the required number. 

According to the question, we have

x + 7  =  25

Here "7" is added to "x". To get rid of 7, we have to subtract 7 on both sides and solve the equation as explained below.  

(x + 7) - 7  =  (25) - 7

x  =  18

Hence, the required number is "18".

Example 4 :

John had some candies. He gave 5 candies to his friend and now he has 18 candies. How many candies did John initially have ? 

Solution : 

Let "m' be the no. of candies that John initially had. 

According to the question, we have

m - 5   =  18

Here "5" is subtracted from "m". To get rid of 5, we have to add 5 on both sides and solve the equation as explained below.  

(m - 5) + 5  =  18 + 5

m  =  23

Hence, John initially had 23 candies.

Example 5 :

The sum of two numbers 22.5. If one number is 7.5, find the other number. 

Solution : 

Let "x' be the other number. 

According to the question, we have

x + 7.5   =  22.5

Here "7.5" is added to "x". To get rid of 7.5, we have to subtract 7.5 on both sides and solve the equation as explained below.  

(x + 7.5) - 7.5  =  22.5 - 7.5

x  =  15

Hence, the other number is 15.

After having gone through the stuff given above, we hope that the students would have understood "Addition and subtraction equations". 

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