Answer: OPTION A
Step-by-step explanation:
Let be "a" the number of adults tickets they sold and "s" the number student of tickets they sold.
With the information given in the exercise you can set up the following System of equations:

Use the Elimination method to solve the system of equations:
1. Multiply the first equation by -6.
2. Add the equations.
3. Solve for "s" in order to find its value.
Then:

4. Finally, substitute the value of "s" into the first equation and solve for "a":

Answer is 279
Step-by-step explanation:
Lets do the following:
How many 1/9 are there in 1? Easy! 9. We can corroborate this by summing 1/9 nine times of multiplying 1/9 nine times. In both cases the result is 9.
Then, how many 1 are there in 31? Easier!! 31. Is we sum the number 1 thirty one times, the result is 31.
Now let join both results:
If each 1 has nine 1/9, and there are thirty one 1s in 31, then in 31 we have 31*9=279 1/9s. This is:
31*1 = 31 * 9 (1/9) = 279 * (1/9)
Here are the areas of the 12 rectangular surfaces that make up the surface area of the podium:
7.5 x 1.5 = 11.25 square feet (Bottom)
1.5 x 1.5 x 2 = 4.5 square feet (Right/Left Bottom Sides)
2.5 x 1.5 x 2 = 7.5 square feet (Right/Left Flat)
1.5 x 1.5 x 2 = 4.5 square feet (Right/Left Top Sides)
2.5 x 1.5 x 2 = 7.5 square feet (Top Front/Back)
2.5 x 1.5 = 3.75 square feet (Top)
7.5 x 1.5 x 2 = 22.5 (Bottom Front and Back)
The area of all these surfaces is 61.5 square feet.
If you mean missing angle, it would be 129.