Risa had a total of 92 pieces of $20 and $2 notes at first. She spent ⁵₇ of the number of $20 notes and received another 7 pieces of $2 notes from her mother. After that, the number of $2 notes she had was ¹₂ of the remaining notes. How much money did Risa have at first?

	$20	$2	Total
Before	7 u	2 u - 7	92
Change	- 5 u	+ 7
After	2 u
Comparing $20-notes and $2-notes	1x2 = 2 u	1x2 = 2 u

The number of $20-notes and $2-notes in the end is the same.

The number of $20-notes in the end is repeated.  Make the number of $20-notes in the end the same. LCM of 1 and 2 is 2.

Number of notes at first
= 7 u + 2 u - 7
= 9 u - 7

9 u - 7 = 92
9 u = 92 + 7
9 u = 99

1 u = 99 ÷  9 = 11

Number of $20-notes at first
= 7 u
= 7 x 11
= 77

Total value of $20-notes at first
= 77 x 20
= $1540

Number of $2-notes at first
= 2 u - 7
= 2 x 11 - 7
= 22 - 7
= 15

Total value of $2-notes at first
= 15 x 2
= $30

Amount that Risa had at first
= 1540 + 30 
= $1570

Answer(s): $1570