Julie had a total of 72 pieces of $10 and $20 notes at first. She spent ³₅ of the number of $10 notes and received another 12 pieces of $20 notes from her mother. After that, the number of $20 notes she had was ¹₂ of the remaining notes. How much money did Julie have at first?

	$10	$20	Total
Before	5 u	2 u - 12	72
Change	- 3 u	+ 12
After	2 u
Comparing $10-notes and $20-notes	1x2 = 2 u	1x2 = 2 u

The number of $10-notes and $20-notes in the end is the same.

The number of $10-notes in the end is repeated.  Make the number of $10-notes in the end the same. LCM of 1 and 2 is 2.

Number of notes at first
= 5 u + 2 u - 12
= 7 u - 12

7 u - 12 = 72
7 u = 72 + 12
7 u = 84

1 u = 84 ÷  7 = 12

Number of $10-notes at first
= 5 u
= 5 x 12
= 60

Total value of $10-notes at first
= 60 x 10
= $600

Number of $20-notes at first
= 2 u - 12
= 2 x 12 - 12
= 24 - 12
= 12

Total value of $20-notes at first
= 12 x 20
= $240

Amount that Julie had at first
= 600 + 240 
= $840

Answer(s): $840