What is the answer and how do you even do this

Refer to interactive solution 17.45 to review a method by which this problem can be solved. the fundamental frequencies of two air columns are the same. column a is open at both ends, while column b is open at only one end. the length of column a is 0.504 m. what is the length of column b?

The lines shown below are parallel. if the green line has a slope of -1, what is the slope of the red line?

How to solve a simultaneous equation involved with fractions?