A 4th grade class took a field trip to a science museum. There are 24 students in the class. Each student purchased a $9 ticket for the museum and a box lunch, which was also $9.
Estimate the total cost of the field trip.

$432

Step-by-step explanation:

Students:24

Ticket:$9

Lunchbox:$9

9+9=18

24x18=$432

{ x + 3 y = 16
  2x - y = 4

Isolate x for x + 3y = 16 :

x = 16 - 3y

Subsititute x = 16 - 3y 

[ 2 ( 16 - 3y ) - y = 4 ]

isolate y for :

2(16 - 3y ) - y = 4

y = 4

For x = 16 - 3y

subsititute y = 4

x = 16 - 3 * 4

x = 16 - 12

x = 4

Solution:

x = 4 and y = 4

hope this helps!.