1. Factor: 7x^2+26xy-8y^2

The answer is (7x-2y)(x+4y) but I can't figure out how!

2. Bernard and Carolyn are refinishing a table. Working alone, Bernard can do the job in 7 hours. If the two work together, the job take 3 hours. How long will it take Carolyn to refinish the table if she works alone?

So far, I have (1/7)(3) + (1/x)(3) = 1