There are 4 students with braces for every 7 students without braces. There are 28 sixth-grade students that have braces at Valley Middle School. How many students are in sixth grade in all?

57

Step-by-step explanation:

28*(7/4)=49

28+49=57

mr. flanders’ class sold 47 doughnuts and   mr. rodriquez’s class sold 38 cartons of milk

step-by-step explanation:

let x be the number of doughnuts sold by mr. flanders’ class and y be the number of cartons sold by mr. rodriquez’s class.

1. together, the classes sold 85 items, then

x+y=85.

2. both classes earn earned $104.49 for their school. if doughnuts were sold for $1.35 each, then x doughnuts costed $1.35x. if cartons of milk were sold for $1.08 each, then y cartons costed $1.08y. hence,

1.35x+1.08y=104.49.

3. solve the system of two equations:

the discriminant is 64 + 4*1*12 = 112

this is prime.

step-by-step explanation: