Elimination Method
2a + b = 13 ……..(1)
3a + 2b = 21…… (2)
Decide which variable you want to
eliminate.
Let us eliminate the variable ‘b’.
Look at the number before ‘b’.
1 and 2.
We have to make these two numbers
equal.
Let us multiply (1) by 2.
(1) x 2 4a +
2b = 26…….(3)
(2) 3a + 2b = 21…… (2)
Now we made the numbers equal. (2, 2)
Look at the sign of the two
numbers. (+2 , +2)
If they are of the same sign (+,+)
or (– , – )
to eliminate ‘b’, we need to subtract the equations.
If they are of different sign, (+, – ),
we need to add the equations.
Since both numbers are of the same sign, we
subtract.
4a + 2b = 26 ……(3)
3a + 2b = 21 ……(2)
(3) – (2),
(4a + 2b) – (3a + 2b) = 26 – 21
4a + 2b – 3a – 2b = 26 – 21
a
= 5
Substitute
a = 5 in (1),
(1) 2a + b = 13
2(5) + b = 13
10 + b = 13
b = 13 – 10
b
= 3
