As given by the question
There are given that the graph of the given statement.
Now,
(a)
One ticket cost will be:
[tex]\begin{gathered} O\text{ne ticket cost=}\frac{150-100}{2} \\ O\text{ne ticket cost=}\frac{50}{2} \\ O\text{ne ticket cost=25} \end{gathered}[/tex]Then,
[tex]\begin{gathered} \text{One ticket cost=100+25} \\ =125 \end{gathered}[/tex]Hence, the cost of one ticket is $125.
Now,
(b)
The money that did the senior class have at the start of the fundraiser is 100.