The correct answer is "His teacher advised it because he did not have time to tutor Euler privately." I just did the assignment and got it correct.
The properties are the commutative, associative, additive identity and distributive properties
D is the only unbiased way, all of the others give information that could affect your opinion
The complete question in the attached figure
we have that
m∠1=<span>58°
</span>m∠7=?
we know that
m∠1+m∠3=180°------------> supplementary angles
and
m∠3=m∠7--------------------> corresponding angles
then
m∠3=180°-m∠1-----------> m∠3=180°-58°=122°
m∠7=m∠3=122°
the answer is m∠7=122°