At the end of August, Roshel had twice as many 20-cent coins as 50-cent coins in her piggy bank. She took out 75 20-cent coins and exchanged it for 50-cent coins of the same value. In September, she saved another 65 20-cent coins and some 50-cent coins. She then had four times as many 50-cent coins in the end. She had 350 coins in the end. How many 50-cent coins did she save in September?

	20-cent	50-cent	Total
Before	2 u	1 u
Change 1	- 75	+ 30
Change 2	+ 65	+ ?
After	1 p	4 p	350

Total number of coins in the end
= 1 p + 4 p 
= 5 p

5 p = 350

1 p = 350 ÷ 5 = 70

Number of 20-cent in the end
= 1 p
= 70

Number of 20-cent at first
= 70 - 65 + 75
= 80

2 u = 80

1 u = 80 ÷ 2 = 40

Number of 50-cent coins in the end
= 4 p
= 4 x 70
= 280

Total value of 75 20-cent coins 
= 75 x 20
= 1500¢

Number of 50-cent coins that was exchanged from 75 20-cent coins 
= 1500 ÷ 50
= 30

Number of 50-cent coins that Roshel saved in September
= 4 p - 1 u - 30
= 280 - 40 - 30 
= 210 

Answer(s): 210