Answer: It will take 15 weeks for Cyndi and her sister to have the same amount of money.
Step-by-step explanation:
Given: Cyndi has $55. Her sister has $115.
Cyndi saves $10 per week. Her sister saves $6 per week.
Let x= Number of weeks.
Total amount of money Cyndi has = 55+10x (i)
Total amount of money sister has = 115+6x (ii)
From (i) and (ii) , we get
[tex]55+10x=115+6x\\\\\Rightarrow\ 10x-6x=115-55\\\\\Rightarrow\ 4x=60\\\\\Rightarrow\ x=\dfrac{60}{4}\\\\\Rightarrow\ x=15[/tex]
Hence, it will take 15 weeks for Cyndi and her sister to have the same amount of money.