Multiples of ten are: 10, 20, 30, 40, 50, 60, & 70.
So there are (7 options that ARE multiplies of ten) out of (75 total options)
Thus, there are (75 - 7 options that are NOT multiples of ten) out of (75 total options).
Answer: 
-4x -6 = -5y + 2
5y = 4x + 6 + 2
5y = 4x + 8
Y = g(x) = 4/5x + 8/5

there are 300 students in the high school.
hope this helps