Atheatre collected $100 from all the 100 attendees in the audience. the prices of the tickets were $10 for adults, $3 for friends of the theatre, and $0.5 for children. there was at least 1 of each ticket sold. how many adults, friends of theatre, and children were in the audience?

i tried to do this with a matrix, but it didn't work out, so how should i approach this?

You can write a system of equations, I'm pretty sure. 
the first equation would be 
10a+3f+.5c=100
and 
a+f+c=100

For the first equation, its the price of each ticket that adds up to 100 tickets
For the second equation, its the amount of people that adds up to 100 people.

I'm pretty sure this is the route to go but I haven't solved it for myself (yet) I'll probably comment the answer if you need me to