Answer:
2 pills of brand X, 2 pills of brand Y and 3 pills of brand Z.
Explanation:
Required Vitamin :
Vitamin A ⇒ 22 unit
Vitamin D ⇒ 18 unit
Vitamin E ⇒ 11 unit
Units of A, D, E per brand :
X 2 1 2
Y 3 2 2
Z 4 4 1
Let 'u' units of X
'v' units of Y
'w' units of Z required
Then,
2u + 3v + 4w = 22 ------(1)
1u + 2v + 4w = 18 ------(2)
2u + 2v + 1w = 11 -------(3)
By solving the linear equation
u = 2, v = 2, w = 3
2 pills of brand X, 2 pills of brand Y and 3 pills of brand Z.