Step-by-step explanation:

I). let the age of sumi be x and her brother be y

so

x = y+9

x - y = 9...........@

in 10 years

x+10= 2( y-10)

x+10 = 2y - 20

2y -x = 30..............@

solving both equations

-y+x = 9

2y -x = 30

on elimination

we get y = 21years

and x by putting the value of

x= 30 years