Five numbers, three darts each, doubles only to finish: ladder #260 asks for 6, 48, 64, 88 and 116.
6 is a straight double: D3. A miss into the single leaves an odd number, so the next dart has to set up a double before you can finish. 48 is a two-dart finish: 8 D20.
64 is a two-dart finish: T8 D20. 88 is a two-dart finish: T16 D20. 116 needs all three darts: T19 19 D20. If the first dart misses its treble, the board will show the new route straight away.
At best the five finishes need 10 darts out of 15. Your result counts the finishes you make first and the darts you used second. The middle finishes decide this ladder. Choose the route that leaves a double after a missed treble; the suggested routes do that wherever they can.