Arithmetic Sequences

1. $\text{An}$ $\text{arithmetic}$ $\text{sequence}$ $\text{adds}$ $\text{the}$ $\text{same}$ $\text{number}$ $\text{each}$ $\text{time.}$
2. $\text{Only}$ $12,16,20,24,\dots$ $\text{has}$ $\text{a}$ $\text{common}$ $\text{difference,}$ $4\text{.}$

Answer: $12,16,20,24,\dots$

1. $\text{The}$ $\text{common}$ $\text{difference}$ $\text{is}$ $-6-(-7)=1\text{.}$
2. $\text{Step}$ $\text{back}$ $\text{from}$ $-7:-7-1=-8\text{.}$

Answer: $-8$

1. $\text{From}$ $17$ $\text{to}$ $-19$ $\text{is}$ $4$ $\text{equal}$ $\text{steps,}$ $\text{so}$ $\text{the}$ $\text{common}$ $\text{difference}$ $\text{is}$ $\frac{-19-17}{4}=-9\text{.}$
2. $\text{So}$ $\text{the}$ $\text{missing}$ $\text{terms}$ $\text{are}$ $8,-1,-10\text{.}$

Answer: $8,-1,-10$