After several generations of unremitting efforts, the key clues of the symbols Δ, Ψ, Λ, and Θ in the figure were finally discovered:

 

1. Δ, Ψ, Λ, Θ represent four different non-negative integers.

2. Δ + Λ = Θ

3. Λ - Ψ = 5

4. Δ + Ψ = 2