2+1/3n=8 is the answer, I believe.
Since the argument of the sine function is x without any scaling factor, the period is 2π, the 1st selection.
Standard form: Ax+By=C
first put in slope-intercept form:
slope = (0+5)/(6-3) = 5/3
pick point D: 0 = 5/3(6)+b -> b= -10
slope-intercept form: y=(5/3)x-10
multiply both sides by 3:
3y=5x-30
put in standard form:
5x-3y=30
If you list all the common factors, (1,2,3,6), you see the highest common factor is 6
