Answer:
Kara's age = 15 years
Step-by-step explanation:
Let Kara's age = n years
Cassie's age = 2n - 3
Sum of their ages = 42
n + 2n - 3 = 42 {Combine like terms}
3n - 3 = 42 { add 3 to both sides}
3n = 42 +3
3n = 45 {Divide both sides by 3}
3n/3 = 45/3
n = 15
Kara's age = 15 years