Ted planted 2 x 50 = <<2*50=100>>100 tomato seeds.
So, Mike and Ted planted 50 + 100 = <<50+100=150>>150 tomato seeds in the morning.
In the afternoon, Ted planted 60 - 20 = <<60-20=40>>40 seeds.
Thus, Mike and Ted planted 60 + 40 = <<60+40=100>>100 tomato seeds in the afternoon.
Therefore, they planted 150 + 100 = <<150+100=250>>250 tomato seed altogether.
#### 250