How to find area and perimeter of a rectangular shape

What is the missing step in this proof ?

School has 204 sixth grade students. if the sixth grade is 30% of the total school, how many students are in the middle school?

Is there a direction u in which the rate of change of f(x,y)equals=x squared minus 3 xy plus 4 y squaredx2−3xy+4y2 at p(1,2) equals 14? give reasons for your answer. choose the correct answer below. a. no. the given rate of change is smaller than the minimum rate of change. b. no. the given rate of change is larger than the maximum rate of change. c. yes. the given rate of change is larger than the minimum rate of change and smaller than the maximum rate of change.