∠M=90°-23.1°=66.9° - it's a right answer.
u=d/sin∠D=97.25
m=cos∠D*u=89.52
Check the picture below, that's the "inscribed angle theorem"

- What is the solution to the inequality -3x-42>3 ?


Add 42 to both sides.

Add 3 and 42 to get 45.

Divide both sides by -3. As -3 is <0, the inequality direction has changed.

Divide 45 by -3 to get -15.

150
explain:
100/28*42=x which turns into x=150
if / means absolute value, then the answer is -3. The absolute value of 3 is 3, then you take the negative value of it, which is -3.
Btw, the absolute sign is ||, not //.