Algebra
posted by Sam .
Hi, here is a question and my answer I have done so far, not sure about the end result so any help appreciated
5a2 (5+4a)=9
Multiply out brackets 5a10+8a =9
Add 10, 5a+8a=1
Collect like terms 13a = 9
Divide by 13 = a =1/13
I am pretty sure the answer should be a = 1/3 but not sure how to get there, , thanks

You have an error in your first step when you multiplied:
2(5 + 4a)
It is not 10 + 8a . 
Salisbury High School decided to take their students on a field trip to a theme park. A total of 150 people went on the trip. Adults pay $45.00 for a ticket and students pay $28.50 for a ticket. How many students and how many adults went to the park if they paid a total of $4770

Please do not append a new question at the end of somebody else posting.
Your question will likely be passed over, since most tutors will not look at a posting if they see that it has been answered.
Your problem:
let number of adult tickets be a
let number of student tickets be 150a
solve:
45a + 28.5(150a) = 4770