In serial connection, the total current in the circuit is a constant.
Thus which ever will have a higher potential through will glow brighter.
in serial circuit, Power is direcly proportional to resistance (P=I2R)
thus 100 W will have higher resistance and since V = IR hence will glow brighter.
In parallel connection, since both of them will have equal potential difference accross them, power will be inversely proportional to resistance as P = V2/R, thus 60 W will have higher resistance. At equal potential the one with more current flowing through it will glow brighter, thus the one with lower resistance i.e 100 W will glow brighter