For matineesa movie theater charges 7 per adult and 4 per ch

For matinees,a movie theater charges $7 per adult and $4 per child.if 84 people attended a matinee and paid a total of $432,How many adults and how many children were there .

First choose to let x=number of adults and y = number of children.
Then you can write 2 equations from the information given.

1) 7x + 4y = 432
2) X + y = 84
Solve equation 2 for x: X = 84