let us repersent the number of student tickets, then 's + 20' is repersenting the number of adult tickets.
The equation for the total tickets can be experssed as the following:
4.00 * s + 8.00 * ( s + 20 ) = 880.00
solving for 's=60', there were 60 student tickets.
60 + 20 = 80
there were 80 adult tickets.
Hope helps!-Aparri
X=4. 4/2=2 and 8/4=2 making the equations equal
Make a change of coordinates:


The Jacobian for this transformation is

and has a determinant of

Note that we need to use the Jacobian in the other direction; that is, we've computed

but we need the Jacobian determinant for the reverse transformation (from

to

. To do this, notice that

we need to take the reciprocal of the Jacobian above.
The integral then changes to
