#7 help please

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

In a graph with several intervals o data how does a constant interval appear? what type of scenario produces a constant interval?

Given a: b and b: c, find a: b: c. write the ratio in simplest form. a: b=6: 10 and b: c=21: 33