What type of reaction is   3ca(oh)2 + al2(so4)3 = 3caso4 + 2al(oh)3 combustion, synthesis, decomposition, single displacement, double displacement, or acid-base neutralization

Answer is: Double Displacement.
Combustion is reaction with oxygen.
Synthesis is reaction of two or more substances combining to make a more complex substance. 
Decomposition is reaction where one substance is broken down into two or more simpler substances. 
Single Displacement is reaction where  neutral element metal or nonmetal become an ion as it replaces another ion in a compound. 
Double displacement reactions (more reactive metals displace metals with lower reactivity).
Neutralizationis is reaction in which an acid and a base react quantitatively with each other.