10% of Cody's savings was $42 more than 30% of John's savings. After Cody spent ²₃ of his savings and John spent 40% of his savings, John had $148 less than Cody. How much was John's saving at first?

	John	Cody
Before	10 u	30 u + 420
Change	- 4 u	- 20 u - 280
After	6 u	10 u + 140
Comparing John and Cody in the end		148 more

10% = ¹⁰₁₀₀ = ¹₁₀

30% = ³⁰₁₀₀ = ³₁₀

¹₁₀ Cody = ³₁₀ John + 42 

Make the numerators the same. LCM of 1 and 3 is 3.
 
1x310x3 Cody = 3x110x1 John + 42 
330 Cody = 310 John + 42 

Simplify the fractions.
¹₃₀ Cody = ¹₁₀ John + 14

Let ¹₁₀ John be 1 u.

John's savings at first = 10 u

¹₃₀ Cody = ¹₁₀ John + 14
Let ¹₃₀ Cody be 1 u + 14.

Cody's savings at first
= 30 x (1 u + 14) 
= 30 u + 420

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

Savings that Cody spent 
= ²₃ x (30 u + 420)
= 20 u + 280 

John had $148 less than Cody in the end. If another $148 was given to John, the amount that each had in the end would be the same.

10 u + 140 = 6 u + 148 
10 u - 6 u = 148 - 140
4 u = 8

1 u = 8 ÷ 4 = 2

Savings that John had at first
= 10 u 
= 10 x 2
= $20

Answer(s): $20