10% of Pierre's savings was $15 more than 30% of Andy's savings. After Pierre spent ²₃ of his savings and Andy spent 40% of his savings, Pierre had $74 more than Andy. How much was Pierre's saving at first?

	Andy	Pierre
Before	10 u	30 u + 150
Change	- 4 u	- 20 u - 100
After	6 u	10 u + 50
Comparing Andy and Pierre in the end		74 more

10% = ¹⁰₁₀₀ = ¹₁₀

30% = ³⁰₁₀₀ = ³₁₀

¹₁₀ Pierre = ³₁₀ Andy + 15 

Make the numerators the same. LCM of 1 and 3 is 3.
 
1x310x3 Pierre = 3x110x1 Andy + 15 
330 Pierre = 310 Andy + 15 

Simplify the fractions.
¹₃₀ Pierre = ¹₁₀ Andy + 5

Let ¹₁₀ Andy be 1 u.

Andy's savings at first = 10 u

¹₃₀ Pierre = ¹₁₀ Andy + 5
Let ¹₃₀ Pierre be 1 u + 5.

Pierre's savings at first
= 30 x (1 u + 5) 
= 30 u + 150

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

Savings that Pierre spent 
= ²₃ x (30 u + 150)
= 20 u + 100 

Pierre had $74 more than Andy in the end. If another $74 was given to Andy, the amount that each had in the end would be the same.

10 u + 50 = 6 u + 74 
10 u - 6 u = 74 - 50
4 u = 24

1 u = 24 ÷ 4 = 6

Savings that Pierre had at first
= 30 u + 150
= 30 x 6 + 150
= 180 + 150
= $330

Answer(s): $330