Boys are ten more than girls, and girls are twenty MINUS ten, which equals ten.

Then, how many boys and girls are there, that is, 20 boys plus 10 girls, which is equal to 30 people.

The formula 20- 10+ 10=30 can also be listed.

The answer is that the number of people going to the amusement park on weekends is thirty.

You can also assume that a woman is X, so a boy is twenty, twenty plus X equals twenty minus ten, and twenty plus a man equals thirty.