Ineed on how to do these types of problems

#1 
Lets x = number of adult tickets
Lets y = number of children tickets

equation 1: 8x + 4y = 5040
equation 2: x + y = 680

solve them by using substitution
 x + y = 680 
 x = 680 - y

substitute  x = 680 - y into  8x + 4y = 5040

8(680 - y) + 4y = 5040
5440 - 8y + 4y = 5040
-4y = 5040 - 5440
-4y = -400
   y = 100

x = 680 - y
x = 680 - 100
x = 580

There were 580 adults and 100 children at the last Miller's home basketball game.

#2
Similar to the #1

Lets x is the number of people riding school bus
Lets y is the number of people riding luxury charter bus

equation 1: x + y = 65
equation 2: 8x + 15y = 611