Which of the following represents the series below? s28=28 ∑ (9k-4) k=1 a)s28=28(5+248/2) b)s28=9(28)-4+(9(1)-4) c)28(5+248) d) (248-5/2)

I will have to make some assumptions here, in the absence of information from you.  One such thing is the number of elements in this series; it seems to be 28.  If that is correct, then you want to sum up the first 28 elements of this series.
                        28                   28            28(28+1)
First focus on ∑ (9k)    =   9[ ∑ k ] = 9 * = (9/2)(28^2+28) = 3654
                       n=1             n=1                      2

Then focus on the 2nd term:
                                   28
                    ∑ 4   =  4∑1    =4(28) = 112
                                   n=1

Then add together 3654 and 112 to obtain the sum of the first 28 terms of this series 9k-4.                 It is 3766.

1. isolate the variable, in this case, d. subtract 35.5 on both sides of the equation.2. 52 subtracted by 35.5 is 16.53. therefore your answer would be d= 16.5this is the basics of pre algebra, isolating variable through adding, subtracting, multiplying, and dividing, if you have any other questions to ask just comment!