Solve this system of equations using substitution.

a + b + c = 180
b = 3a
c = 5a

Find an equation of the line perpendicular to the graph of 28x-7y=9 that passes through the point at (4,1)

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

An energy drink company claims that its product increases students' memory levels. to support its claims, the company issues advertisements claiming that 8 out of 10 people (chosen randomly from across the country) who tried their product reported improved memory. the missing component in this study is a .