The ratio of grade 7's to grade 8's is 5:3. If there are a total of 90 grade 8's, how many total
students are there in grade 7 and 8?

240 students

Step-by-step explanation:

Grade 7 : Grade 8 = 5 : 3

Number of seventh grade students = 5x

Number of Eighth grade students = 3x

3x = 90

x = 90÷3

x = 30

Total students = 5x + 3x = 8x = 8 * 30 = 240

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.