6. there are 90 seats in the school auditorium. the school had a sold out show of their play last weekend, and made $315. the cost of a ticket for an adult was $5.00 and the cost of a ticket for a child is $2.50. which system of equations could be used to determine the number of adults, a, and the number of children, c, that attended the showing of the movie? group of answer choices 2.5a+5c=90 2.5 a + 5 c = 90 a+c=315 a + c = 315 a+c=90 a + c = 90 5a+2.5c=315 5 a + 2.5 c = 315 5a+2.5c=90 5 a + 2.5 c = 90 a+c=315 a + c = 315 a+c=90 a + c = 90 2.5a+5c=315