8 variables are required.
Static Single Assignment(SSA)
A variable cannot appear more than one on the left hand side of assignment operator.
Lets try this definition for the given expression:
q+r/3+s-t×5+u*v/w
here, we have 3 operators, multiplication, addition & division. We have to keep in mind the precedence & associativity of them.
Associativity: left to right
precedence: 1. * & / 2. +
A=r/3
B=t×5
C=u×v
C1=C/w
A1=A+q
A2=A1+s
A3=A2-B
A4= A3+C1
SSA variable set: {A,B,C,A1,A2,A3,A4,C1}
Minimum number of variables=8.