Let us take number of $5 bills = x and
number of $10 bills = y.
Give that "number of $10 bills is twice the number of $5 bills".
So, y is twice of x,
We can setup an equation.
y= 2x ............................... equation(1)
Total value of all bills = $125.
We can setup another equation,
5*(number of $5 bills) + 10*(number of $10 bills) =125.
5(x) +10(y) = 125 ................................... equation(2)
Plugging y=2x in equation(2), we get
5(x) +10(2x) = 125 .
5x+20x = 125.
Adding like terms
25x = 125
Dividing both sides by 25.
25x /25 = 125/25
x= 5.
Plugging x=5 in first equation, we get
y= 2(5) = 10.
Therefore, number of number of $5 bills=5 bills and number of $10 bills = 10 bills.
