Question

one sister is 6 year elder to her brother two third of the sisters age is three years more than three fourth of the brother age how old are the brother and sister

Answer 1

let the brother present age be x year
then sister's age be (x+6) year
ATQ
$\frac{2}{3} (x + 6) = \frac{3}{4} x + 3$
$8(x + 6) = 3(3x + 12)$
8x+48=9x+36
9x -8x=48-36
x=12

brother's age= 12 year