S10=2a1+9d
*2=(2a1+9d)*5=(2a1+9*6)*5=240
2 10a1+270=340
10a1=340-270
10a1=70
a1=7
a10=a1+9d
a10=7+9*6
a10=7+54
a10=61
S10=2a1+9d
*2=(2a1+9d)*5=(2a1+9*6)*5=240
2 10a1+270=340
10a1=340-270
10a1=70
a1=7
a10=a1+9d
a10=7+9*6
a10=7+54
a10=61