Alain was given 50 envelopes
Brenda was also given 50 envelopes
Let the time taken by Alain to address 50 envelopes = a minutes
Let the time taken by Brenda to address 50 envelopes = b minutes
Question => how much time did it take Alian to address the envelopes he was given?
Statement 1 => Alian addressed his envelopes in 1.2 times the amount of time it took Brenda to address her envelopes.
a = 1.2b minutes, the exact value of b is unknown. Statement 1 is NOT SUFFICIENT

Statement 2 => if Alian and Brenda had addressed 50 envelopes together, each working at the same rate as when they worked separately, it would have taken them 1 hour and 50 minutes to address all the envelopes.
$$work rate=\frac{workdone}{time}$$
$$For\ Alian\ work rate\ for\ 50\ envelopes=\frac{50}{a}$$
$$Therefore,\ work\ rate\ for\ 1\ envelope=\frac{1}{a}and\ Brenda=\frac{1}{b}$$
1 hour 50 minutes = 60 minutes + 50 minutes = 110 minutes
For Brenda and Alian to work today in 50 envelopes with their present work rate,
$$._.^.\ \frac{1}{a}+\frac{1}{b}=\frac{1}{110}$$ but the value of b is still unknown. So, statement 2 is NOT SUFFICIENT

Combining both statements together =>
a = 1.2b
$$\frac{1}{a}+\frac{1}{b}=\frac{1}{110\ }\ \ where\ a\ =\ 1.2b$$
$$Therefore,\ \frac{1}{1.2b}+\frac{1}{b}=\frac{1}{110}$$
$$\frac{1+1.2}{1.2b}=\frac{1}{110}$$
$$\left(2.2\right)\cdot110=1.2b$$
$$\frac{242}{1.2}=\frac{1.2b}{1.2}$$
$$b=201.7\approx202\min utes$$
Back to a = 1.2b where b = 201.7
a = 1.2 * 201.7
a = 242 minutes

Both statements together ARE SUFFICIENT
Answer = C