Åk 6–9
 
English/عربي

3.1 Addition and Subtraction
When you solve more advanced equations, you will discover that it is a good idea if you learn methods to solve the equations step by step.

Don’t forget that it is very important that you keep in mind that the equal sign means that there should be exactly the same quantity on both sides of the equal sign.

If you do a calculation on one side, you must also do that same calculation on the other side.

Example:

x + 12
=
18
Left Hand Side
(LHS)
Right Hand Side
(RHS)




An equation can be compared to a balance scale where each of the pans weighs the same.

The equation that we illustrate with the scale is 3 = 2 + x



Bild: Hogia AB, Multimediabyrån


Subtracting with the same number on both sides

Example: Solve the equation x + 7 = 13

Solution:

We want to get x by itself on the LHS.

x + 7 = 13

x + 7 – 7

=

13 – 7


x = 6


Bilder: Hogia AB, Multimediabyrån





Adding with the same number on both sides

Example: Solve the equation y – 6 = 11


Solution:

We want to get y by itself on the LHS.

y – 6 = 11

y – 6 + 6

=

11 + 6


y = 17



Bilder: Hogia AB, Multimediabyrån