Icy Helium
Icy Helium is the first level of day 3 and the 7th level overall in Bloons Festive Fun.
Solution
Aim a fully powered dart at the Helium Bloon, then when the frozen Helium bloon is near the height of the topmost metal blocks, aim a fully powered dart at the frozen bloon and it should bounce and pop the Tack Bloon.