Answer:
Part A: [tex]k=s-4[/tex]
Part B: 17 years old.
Step-by-step explanation:
Let be "k" Katie’s age, and "s" Sylvia’s age.
Part A
According to the information given, Katie is 4 years younger than Sylvia. This meanas that we can find Katie's age subtracting 4 years from Sylvia's age.
Therefore, we can write the following equation that shows the relationship between Katie’s age and Sylvia’s age:
[tex]k=s-4[/tex]
Part B
In order to find Sylvia’s age when Katie is 13 years old, you must substitute [tex]k=13[/tex] into the equation and then solve for "s":
[tex]13=s-4\\\\13+4=s\\\\s=17[/tex]