Can some one me with the questions?

Notice that x+4 is one of the denominators, and that x(x+4) is the LCD.
                      x
Thus, mult. by x(x+4), obtaining  x^2.  
                    x+4
Next, mult. [ 1/x + 1/(x+4) by x(x+4), obtaining   x+4 + x = 2x+4 or 2(x+4)
                                                                x^2
Then the simplified fraction becomes 
                                                              2(x+4)

Generally allows you to post only 1 or 2 questions at a time.  I will do #15 as a courtesy to you, but want you to try #16 yourself (or to post it separately).

-4, 2, 8, 14, ...  is an arithm. seq.  Every new term is equal to the previous term, plus 6:  -4+6 = 2; 2+6=8, and so on.  Thus:  first term is a = -4; common difference is d = 6

a(50) = a(1) + (50-1)(6), or   a(50) = -4 + (49)(6) = 290 (answer)