Q28: How much does the white ball weigh?

This is really easy puzzle for brain teaser.

Lets define red ball as “R” and white ball as “W”

so it is asked how much W ball weighs.

so we see on image that 2W+R =3R+30

it is obvious that on small scale 3R=30, so R ball weighs 10

if we put 10 instead of R;

2W+10=3*10+30

2W=60-10

W=25

so ANSWER is 25