Since the length of wire used for 4 small stars is the same as that for 3 large stars, the number of small stars that can be made with the same length of wire used to make 18 large stars is:
(18 ÷ 3) x 4 = 24 small stars

Let's find the length of wire he needs to make the remaining stars.

Since we can make 24 small stars with the same length of wire used to make 18 large stars, then 12.24m of wire makes 24 + 10 small stars.

12.24m → 34 small stars
1 small = 12.24m ÷ 34 = 0.36m

The remaining stars are 12 large stars and 15 small stars. Since 12 large stars is equivalent to (12 ÷ 3)*4 = 16 small stars, the remaining stars to make are 16 + 15 small stars.

16 + 15 = 31
31 x 0.36m = 11.16m