Let's set up an equation to solve for the interest rates.
Let X% be the interest rate for the first bank and Y% be the interest rate for the Union bank.
According to the information given, Victory earned a total interest of #640 in one year with the initial savings of 3,000 Naira in the first bank and 2,000 Naira in the Union bank. This can be expressed as:
(3000 * X/100) + (2000 * Y/100) = 640
Additionally, if Victory had saved 2,000 Naira in the first bank and 3,000 Naira in the Union bank for the same period, she would have earned an extra 20 Naira as additional interest. This can be expressed as:
(2000 * X/100) + (3000 * Y/100) = 640 + 20
Simplifying the equations, we have:
30X + 20Y = 640 (Equation 1)
20X + 30Y = 660 (Equation 2)
To solve this system of equations, we can use the elimination method or substitution method. Let's use the elimination method:
Multiplying Equation 1 by 3 and Equation 2 by 2, we have:
90X + 60Y = 1920 (Equation 3)
40X + 60Y = 1320 (Equation 4)
Subtracting Equation 4 from Equation 3, we get:
90X - 40X = 1920 - 1320
50X = 600
X = 12
Substituting the value of X into Equation 1, we can solve for Y:
30(12) + 20Y = 640
360 + 20Y = 640
20Y = 280
Y = 14
Therefore, the value of X is 12% and the value of Y is 14%.