Question

mary is twice older than her sister. in 5 years time she will be 2 years older than her sister.find how old are they both?

Answer 1

x+2+5= 2x+5
x+7= 2x+5
x=2
so mary is 2 yrs old and her sister is 4 years old

Answer 2

Let mary's age be x
let her sister's age be y

According to the question 2x=y
x+5=5+2+y
x+5=7+y
x+5=7+2x
2x-x=7-5
Therefore X=2
2x=y
y=4