Checking out 151

The standard route

T20 T17 D20

After the first dart

leaves 91 — T17 D20

After the second dart: leaves 40 — D20

If the first dart misses

• T19 T18 D20
• T20 T19 D17
• T19 T20 D17

With two darts

There is no two-dart finish from here.