Question

My sister is 8 years older than I am. The sum of our ages is 28. Find our ages.

I am years old. My sister is years old.

Answer 1

My sister is

18

years old.

Explanation:

s = m + 8 Eq. 1

s + m = 28 Eq. 2

s = my sister age

m = my age

Replacing Eq. 1 in Eq. 2:

(m+8) + m = 28

2m + 8 = 28

2m = 28 - 8

2m = 20

m = 20/2

m = 10

From Eq. 1:

s = m + 8

s = 10 + 8

s = 18

Check:

from Eq. 2:

s + m = 28

18 + 10 = 28