Answer:
Mary is 4 and her sister is 2
Step-by-step explanation
We can denote Mary's sister as x and Mary as 2x
M's Sister: x
Mary: 2x
They said in 5 years she will be 2 years older.
In 5 years
M's Sister: x+5
Mary: (x+5)+2
Now we create an equation
2x+5=(x+5)+2
2x+5=x+5+2
2x+5=x+7
Subtract 5 from both sides
2x=x+2
Subtract x from both sides
x=2
So now Mary's sister is 2 and Mary is 4.
Check:
2+5=7
4+5=9
9-7=2
So the answer is correct.
Hope this helps.