I have a list

```
lista={a1,a2,a3,a4,a5,a6,a7,a8,a9}

```

I'm trying to get the arithmetic progression using `Solve` with the following rules:

```
Solve[a3+a6==34&&a4+a9==50, {a1,a2,a3,a4,a5,a6,a7,a8,a9}]

```

Is there anything smarter to apply?