1. What is the sum of the first 19 terms of the arithmetic series?

3 + 8  + 13 + 18

The 19th term is given by

3 + 5(19-1)  =  3 + 5(18)  =  93

And the sum is given by

[ 93 + 3]  (19/2) =

96/2  * 19 =

48 * 19  = 

912

The second isn't showing up for me

For the third, we have

(n) (n + 1)        where n  =  75

75 * 76   =

5700