Question

Does anyone help me about chemical reactions?
1-Synthesis reactions
2-Decomposition reactions
3-dual-exchange reactions
4-displacement reactions

Answer 1

SYNTHESIS
element + element => compound

DECOMPOSITION
compound => element + element

SINGLE REPLACEMENT
AX + B => BX + A

DOUBLE REPLACEMENT
AX + BY => AY + BX

Sorry idk which 3/4 correspond to this is just how i learned it :)