In Static Single Assignment when we assign the values, the variables to which the value is being assigned should be unique.
$T1 = u - t$
$T2 = T1 \ast v$
$T3 = T2 +w$
$T4 = t-z$
$T5 = t3 \ast t4$
So $T1 \ldots T5 =5 + (u,t,v,w,z)=5$
Total 10 variables.
Note: RHS of the operation can use the previously used variables, but LHS in SSA must always be unique.