Data flow equations to determine value dependencies I need to define the data-flow analysis equations to determine the value dependencies of an statement.

For example:

a = 9 
b = a + 7
c = b * 2


the value of c depends on the value of a.

I'm sure this is a well known problem in data flow analysis, can any one point to the equations solving this? Static Single Assignment (SSA) form can be used.
Well, it seems that this can be reduced to the Reaching Definition problem, who's equations are:

$REACH_{in}(S) = \bigcup_{p \in pred(S)} REACH_{out}(p)$ 

$REACH_{out}(S) = GEN(S) \cup (REACH_{in}(S) - KILL(S))$

$GEN[d: y \rightarrow f(x_1, .., x_n)] = {d}$ 

$KILL[d: y \rightarrow f(x_1, .., x_n)] =DEFS(y) - {d}$