For a)
Before
Rachel : Timothy
12 : 13
After
Rachel : Timothy
3 : 1
In order to have the same amount for Rachel
12: 4
Timothy
13units -4 units =9 units
9units=$27
1 unit=27/9
1unit = $3
For Rachel
Rachel saved $36
b)
Total units at first =12+13=25
If 1units is $3
25 units is 3x25
25 units is $75
They saved together 75
ANSWER
Rachel saved $36
They saved together 75