Answer:
July 4th of the next year will be on a Monday.
Explanation:
We have the following "circular" sequence of days:
{Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday}
When it is a leap year, days jump two positions.
For example, Wednesday to Friday, Friday to Sunday.
For example, 2020 is a leap year. In 2019, September 8 was on a Sunday. This year is going to be on a Tuesday.
When it is not a leap year, days jump one position
So Saturday to Sunday, Sunday to Monday...
2019 was not a leap year. September 8, 2018 was a Saturday. In 2019, it was a sunday.
So
July 4th of the next year will be on a Monday.