Tickets for a school event were $2.25 for students and $3.75 for parents. if a total of 70 tickets were sold for $205.50, how many student and parent tickets were sold?

Let s and p be students and parents. Then:
s+p=70
2.25s+3.75p=205.50
Solve for s and p. ☺☺☺☺

I would use simultaneous equations for this. 
let the number of student tickets be s and parents tickets be p.
s + p = 70 .      (1)
2.25s + 3.75p = 205.5 .    (2)
from (1),
s = 70 - p .    (3)
sub (3) into (2)
2.25(70-p) + 3.75p = 205.5
157.5 - 2.25p + 3.75p = 205.5
157.5 + 1.5p = 205.5
1.5p = 48
p = 32
now sub p = 32 into (1)
s + 32 = 70
s = 38
therefore students tickets sold 38 and parents tix sold 32.