33. For this problem you have to sole the following system of equations.
x+y=531
5.75x+1.25y=2013.75
After you solve the system of equations you get that
x=300, y=231
Therefore 300 full-price tickets were sold.
34. Since water is not acid, you have to solve the following equation
0*Water + 0.40*50 = 0.30*(Water+50)
After you solve the equation you get
Water = 16.67
So, you have to add 16.67 ML of water.
and that's the solution for 34.
35.
The next problem is very easy, notice that 12/6 = 2 and 4/6 = 0.666666=0.67 , therefore the scale factor would be 6. And that would be it.