Answer:
I'm not sure if this will be able to help, though I found the same question, but answered by someone who is far more advanced with this, and has answered for more questions than I have. Hope this can help, if not please comment, so I can delete.
brainly.com/question/21188240
Use Desmos it helps you with questions like that
You might need a maths degree for this one, I believe it’s 4 but don’t quote me on that.
They have $49.00 left for desert because a ticket is $15 for each person 7 and older. So 15 × 3 people = $45.00. $1.50 per slice and they got 4 slices so 1.50 × 4 = $6.00. $45.00 + $6.00 = $51.00. $100 - $51 = $49.00