30% of tickets sold by a movie theater for the Friday night show, their children's tickets at 4 dollars each. The rest of the tickets were sold at the full price of $8.50. The movie theatre collected $252 for the children's tickets. How many tickets did they sell in all?

4*0.3*x = 252

this is the price of a ticket (4) multiplied by the percentage of tickets (0.3 = 30%), multiplied by the total number of tickets sold (x)

find x.

I don't understand why you are given the price of an adult ticket, you don't need it unless you have stated the question wrongly or I have interpreted it wrongly.