Question

Purnima's grandfather is 7 years elder to
her grandmother. The sum of one-eighth of
her grandfather's age and one-ninth of her
grandmother's age equals 20 years. How old are
Purnima's grandparents?​

Answer 1

Answer:

Step-by-step explanation:

Let grandfather's age = x years

Let grandmother's age = y years

x - y = 7

x = 7 + y

x/8 + y/9 = 20

After substituting x by y+7, we get  (7+y)/8 + y/9 = 20

9(y+7)/9(8) +8y/8(9) = 20

(9y+63)/72 +8y/72 = 20

(9y+63+8y)/72 = 20

9y+8y+63 = 20(72)

63 + 17y = 1440

17y = 1377

y = 81 years

x = 7 + 81

x = 88 years (Ans.)