s15=15(a1+a9+14d)2
a7=27
d=a9-(a7+d)
2d=-6
d=-3
a9=a1+8d
a1=45
a14=45+13*(-3)=6
a11=45+10*(-3)=15
a14/a11=6/15
s15=15(a1+a9+14d)2
a7=27
d=a9-(a7+d)
2d=-6
d=-3
a9=a1+8d
a1=45
a14=45+13*(-3)=6
a11=45+10*(-3)=15
a14/a11=6/15