"The school sold 8 adult tickets and 5 child tickets for a total of $104", we can express it as follows

"On the second day they sold 4 adult tickets and 6 child tickets for a total of $80", we can express it as follows

These two equations form a linear system of equations, which we can solve by multiply the second equation by -2

Then, we combine the equations

Now, we find x

According to this solution, each adult ticket costs $8 and each child ticket costs $8.
If they sold 10 adult tickets and 4 child tickets on the third day, then they made

If they sold 22 adult tickets and 8 child tickets on the last day, then they made

Hence, they made $128 more on the last day than the third day because that's the difference.