Let us take the first equation first
2a + b = 5
Then
b = 5 - 2a
Now we have to put the value of b from the first equation in the second equation. Let us take the second equation now.
3a + 2b = 9
3a + 2(5 - 2a) = 9
3a + 10 - 4a = 9
- a = 9 - 10
- a = - 1
a = 1
Now let us put the value of a in the first equation.
2a + b = 5
2(1) + b = 5
2 + b = 5
b = 5 - 2
= 3
So the value of the unknown variable a is 1 and the value of the unknown variable b is 3.
