2. a13=a1+d(13-1)
a13=3+4*12=51
a13=51
3. a8=a1+d(8-1)
a8=9+3*7=9+27=36
a8=36
4. a12=a1+d(12-1)
a12=-7+3*11=-7+33=26
a11=26
5. a6=a1+d(6-1)
a6=-7+1*5=-7+5=-2
a6=-2
6. a9=a1+d(9-1)
a9=10+3*8=10+24=34
a9=34
7. a7=a1+d(7-1)
a7=-9+4*6=-9+24=15
a7=15
8. a7=a1+d(7-1)
a7=-4+(-2)*6=-4+(-12)=-16
a7=-16
9. a10=a1+d(10-1)
a10=3+2*9=3+18=21
a10=21