Question

At a county fair, adults' tickets sold for $5.50, senior citizens' tickets for $4.00, and children's tickets for $1.50. On the opening day, the number of children's and senior's tickets sold was 30 more than half of the number of adults' tickets sold. the number senior citizens' tickets sold was 5 more than four times the number of children's tickets. How many of each type of ticket were sold if the total receipts from the ticket sales were $14, 970?

Answer 1

let a = no. adult tickets
let s = no. senior tickets
let c = no. child tickets

c + s = 30 + 1/2 a
s = 5 + 4c
5.5a + 4s + 1.5c = 14970

I'll leave the solution to you. Substitution, Gaussian elimination, determinants, whatever.