1. Subtract unlike rational numbers

2. Rational numbers
A rational number is a number that can be expressed in the form
where p and q are integers and q ≠ 0.
Numerator
Denominator
For example are rational numbers
NOTE:
A rational number is said to be in standard form if its
denominator is positive and the numerator and
denominator have no common factor other than 1.
If a rational number is not in the standard form, then it can
be reduced to the standard form.

3. + ( + ) = + + ( - ) = - - ( - ) = + - ( + ) = -
Rules of Addition and subtraction
Rule 1
Two numbers have same sign
Add the numbers
Copy bigger number sign
Rule 2
Two numbers have different sign
Subtract the numbers
Copy bigger number sign
Rules of multiplication
Converting 2 symbols into 1
Rule 1
Multiply same sign  Answer is +
+ ( + ) = +
- ( - ) = +
Rule 2
Multiply different sign Answer is –
+ ( - ) = -
- ( + ) = -

4. Least Common Multiple(Recap)
Least Common Multiple (LCM) is the smallest Number that can divide 2
numbers without leaving a reminder
LCM can be found by Prime Factorization method.
Example: Find the LCM of 20 and 28.
The LCM of 24 , 28 = 2 X 2 X 5 X 7
= 140
Find if the two numbers are commonly divisible by 2,3,5,7,11,13,17

5. Denominator is different, using LCM method to find common denominator
Example 1: Subtract
Solution:
Step 1 –
Denominator is different, using LCM method to find
common denominator
LCM (8,11)
= 11 x 8 = 88 11
x 11
x 8
Step 2 – Rewrite fractions with denominator of 12
X 11
x 8
Step 3 – Rewrite fractions with common
denominator
Step 4 – Add fractions with like denominator
By addition rule, both signs are same then add and put bigger number’s sign
Answer :

6. Step 3 – Rewrite fractions with denominator of 30
Example 2: Subtract
Solution:
Step 1 – The sign in the middle (i.e., operation sign) and the sign of
the second number to be made into single sign based on sign rule
below
By rule, - (-) = +
LCM (36,9)
= 9 x 4 = 36 9
Step 2 – Denominator is different, using LCM method to find
common denominator
x 1
x 4
Step 3 – Rewrite fractions with denominator of 30
x 1
x 4
Step 4 – Rewrite fractions with common
denominator
Step 5 – Add fractions with like denominator
Answer :

7. Solution: Writing the given statement mathematically
Example 3: Subtract
from
Solution: Writing the given statement mathematically
Step 1 – The sign in the middle (i.e., operation sign) and the sign of
the second number to be made into single sign based on sign rule
below
By rule, - (-) = +
LCM (5,15)
= 5 x 3 = 15 5
Step 2 – Denominator is different, using LCM method to find
common denominator
x 3
x 1
Step 3 – Rewrite fractions with denominator of 30
x 3
x 1
Step 4 – Rewrite fractions with common
denominator
Step 5 – Add fractions with like denominator
By addition rule, both signs are different then subtract and put bigger number’s sign
Answer :

8. Try these
1. Subtract
2. Subtract
3. Subtract
from