10% of Justin's savings was $57 more than 30% of Charlie's savings. After Justin spent ¹₂ of his savings and Charlie spent 40% of his savings, Justin had $303 more than Charlie. How much was Justin's saving at first?

	Charlie	Justin
Before	10 u	30 u + 570
Change	- 4 u	- 15 u - 285
After	6 u	15 u + 285
Comparing Charlie and Justin in the end		303 more

10% = ¹⁰₁₀₀ = ¹₁₀

30% = ³⁰₁₀₀ = ³₁₀

¹₁₀ Justin = ³₁₀ Charlie + 57 

Make the numerators the same. LCM of 1 and 3 is 3.
 
1x310x3 Justin = 3x110x1 Charlie + 57 
330 Justin = 310 Charlie + 57 

Simplify the fractions.
¹₃₀ Justin = ¹₁₀ Charlie + 19

Let ¹₁₀ Charlie be 1 u.

Charlie's savings at first = 10 u

¹₃₀ Justin = ¹₁₀ Charlie + 19
Let ¹₃₀ Justin be 1 u + 19.

Justin's savings at first
= 30 x (1 u + 19) 
= 30 u + 570

Savings that Charlie spent
= 40% x 10 u
= ⁴⁰₁₀₀ x 10 u
= 4 u

Savings that Justin spent 
= ¹₂ x (30 u + 570)
= 15 u + 285 

Justin had $303 more than Charlie in the end. If another $303 was given to Charlie, the amount that each had in the end would be the same.

15 u + 285 = 6 u + 303 
15 u - 6 u = 303 - 285
9 u = 18

1 u = 18 ÷ 9 = 2

Savings that Justin had at first
= 30 u + 570
= 30 x 2 + 570
= 60 + 570
= $630

Answer(s): $630