Mike started by throwing 20 seeds to the birds and then threw twice as many, 20 + 20(2) = 20 + 40.
That totals to 20 + 40 = <<20+40=60>>60 seeds.
He also threw 30 other seeds and had 30 left over, which means he started with 60 + 30 + 30 = <<60+30+30=120>>120 seeds.
#### 120