How to solve m/3n + 2/7n , I know the answer is 7n+6/21n but How did you get there? the app im using only says "cross multiply" to which iam getting 7nm+6n/21n^2.please fast

Hey Nate!was hoping you could verify the steps used in this algebra hw so I can have a reference as I teach my sonthanksalgebra practice.docx 

A graph from the news media that you think may be closely modeled by a linear, quadratic, polynomial, rational, logarithmic, or exponential function If you are using an electronic resource, either provide the link or scan and upload it. Make sure you scan as one of the following file types: *.bmp, *.gif, *.jpg, *.jpeg, and *.png. An explanation of which type of function the graph most closely modelsA detailed description of the behavior of your chosen graph, such as increasing and decreasing intervals, max or min values, intercepts, domain and range, end behavior, symmetry, even or odd behavior, the type of equation, asymptotes, and restricted values Does your graph go through the origin? Does it have an x-intercept and/or a y-intercept? Why or why not? At what x-values does the graph rise or fall? Is there a reason behind the behavior of the graph? More detail is better.