For any Booleans a and b, the following truth table applies:
a |
b |
a→b |
F |
F |
F |
F |
T |
T |
T |
F |
F |
T |
T |
T |
Therefore P→R (if P, then R) is equivalent to R; and Q→S is equivalent to S.
S∨R is equivalent to R∨S (commutativity of the Boolean-OR operation).
P∨Q≡R∨S≡(P→R)∨(Q→S).