Question 845652
Just translate directly into symbols.

Let n be "a number".
{{{highlight(highlight(6n*15=42))}}}----------that's it.
... the only real problem is the ambiguity in your description.  


The imprecise language does not distinguish between (6n)+15 and 6(n+15).  Where is the boundary of the "and"?  Does the description want to mean, 6*n*15?  That is, product of 6, n, and 15?


Not really a good exercise problem because it is not precise.