20% of Owen's savings was $24 more than 40% of Mark's savings. After Owen spent ³₁₀ of his savings and Mark spent 40% of his savings, Mark had $148 less than Owen. How much was Mark's saving at first?

	Mark	Owen
Before	5 u	10 u + 120
Change	- 2 u	- 3 u - 36
After	3 u	7 u + 84
Comparing Mark and Owen in the end		148 more

20% = ²⁰₁₀₀ = ¹₅

40% = ⁴⁰₁₀₀ = ²₅

¹₅ Owen = ²₅ Mark + 24 

Make the numerators the same. LCM of 1 and 2 is 2.
 
1x25x2 Owen = 2x15x1 Mark + 24 
210 Owen = 25 Mark + 24 

Simplify the fractions.
¹₁₀ Owen = ¹₅ Mark + 12

Let ¹₅ Mark be 1 u.

Mark's savings at first = 5 u

¹₁₀ Owen = ¹₅ Mark + 12
Let ¹₁₀ Owen be 1 u + 12.

Owen's savings at first
= 10 x (1 u + 12) 
= 10 u + 120

Savings that Mark spent
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u
= 2 u

Savings that Owen spent 
= ³₁₀ x (10 u + 120)
= 3 u + 36 

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

7 u + 84 = 3 u + 148 
7 u - 3 u = 148 - 84
4 u = 64

1 u = 64 ÷ 4 = 16

Savings that Mark had at first
= 5 u 
= 5 x 16
= $80

Answer(s): $80