This problem is modeled on the example worked in §3.1 of Lomax & Hahs-Vaughn.

Use this small data set:
X1=7\displaystyle {X}_{{1}}={7},     X2=5\displaystyle {X}_{{2}}={5},     X3=5\displaystyle {X}_{{3}}={5},     X4=2\displaystyle {X}_{{4}}={2},
X5=2\displaystyle {X}_{{5}}={2},     X6=2\displaystyle {X}_{{6}}={2},     X7=4\displaystyle {X}_{{7}}={4},     X8=3\displaystyle {X}_{{8}}={3}


Please find i=18Xi=\displaystyle {\sum_{{{i}={1}}}^{{8}}}{X}_{{i}}=

Please find i=16Xi=\displaystyle {\sum_{{{i}={1}}}^{{6}}}{X}_{{i}}=

Please find i=57Xi=\displaystyle {\sum_{{{i}={5}}}^{{7}}}{X}_{{i}}=