no 19 caranya gimana y ka??

3x + 2y = 4 | x1 | 3x + 2y = 4
4x - y = 9 | x2 | 8x - 2y = 18
-------------------- +
11x = 22
x = 2

4x - y = 9
4(2) - y = 9
8 - y = 9
- y = 1
y = -1

a = x = 2
b = y = -1

a - b = 2 - ( -1 )
= 2 + 1
= 3

x=a dan y=b
3a + 2b = 4 [x1] 3a + 2b = 4
4a - b = 9 [x2] 8a - 2b =18 +
--------------------------------------
..................................11a = 22
.....................................a = 2

3 a + 2b = 4
3(2) + 2b = 4
6 + 2b = 4
2b= 4 - 6
2b= - 2
b= -1
nilai a - b = 2 -(-1)
= 3. ....D