Exercițiu 3,va rog, urgenttttt

a3=a1+2r=12, => a1=a3-2r
a6=a1+5r=30
a6-a3=a1+5r-a1-2r=30-12=18
3r=18 => r=6
a1=a3-2·6=12-12
a1=0
a10=a1+9r=9·6
a10=54