How does understanding place value you to subtract across zeros

I'm not sure what you mean by "across zeros" but knowing your place value helps you a lot. For example:
"What is the value of 6 in the number 2,650?"
You would say,
"The value of 6 in the number 2,650 is 600, because it is in the hundred's place."
Make sure you say hundreds and not hundredth's, because the hundredths is behind a decimal. Hope this helped! :)

10 will be the number of adult tickets and 11 will be the number of children tickets. i hope i could ! good luck : )