Araba is 3 years younger means when you add 3 years to Araba's age, you will get the sister's ageLet x= Araba's ageThe sister's age =x+3Sum means addition.If the sum of their ages is 17 years means when you add their ages, you will get 17Araba's age + Sister's age =17x+x+3=172x=17−32x=14Divide both sides by 2x=214=7∴ Araba's age =7 years