Answer:
Let A ⇒apple, B⇒ banana and C⇒carrot
Monday ⇒buy 1 apple, 1 banana, and 1 carrot ⇒ all for €15
∴ A + B + C = 15 ⇒ (1)
Tuesday ⇒buy 3 apples, 2 bananas, 1 carrot ⇒ all for €28
∴ 3A + 2B + C = 28 ⇒ (2)
Wednesday ⇒buy 2 apples, 1 banana, 2 carrots ⇒ for €23
∴ 2A + B + 2C = 23 ⇒ (3)
Using the equations (1), (2) and (3)
A[A/B/C] = [SMon/STue/SWed]
[tex]\left[\begin{array}{ccc}1&1&1\\3&2&1\\2&1&2\end{array}\right] \left[\begin{array}{ccc}A\\B\\C\end{array}\right] =\left[\begin{array}{ccc}15\\28\\23\end{array}\right][/tex]
So, the matrix A = [tex]\left[\begin{array}{ccc}A11&A12&A13\\A21&A22&A23\\A31&A32&A33\end{array}\right] =\left[\begin{array}{ccc}1&1&1\\3&2&1\\2&1&2\end{array}\right][/tex]
And The vector S = [tex]\left[\begin{array}{ccc}SMon\\STue\\SWed\end{array}\right] =\left[\begin{array}{ccc}15\\28\\23\end{array}\right][/tex]
Solving the system of equations:
So, A = 3 , B = 7 and C = 5
So, the price of one Apple = €3
The price of one Banana = €7
The price of one Carrot = €5