Pls i need help with this

Im so bad at fractions they are not my best math thing to work on

At the movie theatre, child admission is $5.20 and adult admission is $9.70. on sunday three time as many adult tickets as child tickets were sold, for a total sales of $788.90. how many child tickets were sold that day?

What number can each term of the equation be multiplied by to eliminate fractions before solving ? 6-3/4x+1/3=1/2x+5