12 is the number of $10 bills
20 is the number of $20 bills
<u><em>Step-by-step explanation:</em></u>
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Hello,
<u>Let's note</u>
a the number of $10 bills
b the number of $20 bills
The total value is $520 so we can write the first equation (1)
We know that there are 32 bills in total so we can write the second equation (2)
(1) - 10*(2) gives
10a + 20b - 10(a+b) = 520 - 320 = 200
10a + 20b - 10a - 10b = 10b = 200
So b = 200/10=20
and then from (2) a = 32 - 20 = 12
Hope this helps.
Do not hesitate if you need further explanation.
Thank you