Question

a brother is 12 years older than his sister. four years ago, the brother was 3 times as old as the sister is now. how old is the broter now? a 12 b 14 c 16 d 18

Answer 1

C. 16

Explanation:

Let the brother's age be x.

Let the sister's age be y.

x = y + 12

x - 4 = 3y

Put x as y + 12 in the second equation.

y + 12 - 4 = 3y

y + 8 = 3y

8 = 3y - y

8 = 2y

y = 4

Put y as 4 in the first equation.

x = 4 + 12

x = 16

The brother is 16 years old and the sister is 4 years old.

Answer 2

C. 16

Explanation:

Brother - b years now.

Sister - s years now.

A brother is 12 years older than his sister.

b - s = 12

(b - 4) - brother 4 years ago.

Four years ago, the brother was 3 times as old as the sister is now.

b - 4 = 3s

b - s = 12 ----> s = b - 12

b - 4 = 3s

b - 4 = 3(b - 12)

b - 4 = 3b - 36

36 - 4 = 3b - b

32 = 2b

b = 16