Use the relationship between the angles in the figure to answer the question.

which equation can be used to find the value of x?

drag and drop the equation into the box.

We know that the angles add to a 180° angle. 
We get the equation then:

And the above equation is equivalent to this one:

A straight line is 180° no matter how many times it is divided

So ..

31° + x° + 40° = 180°
71° + x ° = 180°
x° = 180° - 71°
x° = 109°

If you need an equation, it would be y=2x+8, y would be how long it grew, x being weeks.if you need how long he was asleep, it would be 4 weeks if he started with no beard, the equation would be x=8÷2if he did have a beard before hand, the equation would be 2w+x=8