Top left because for any x, there can only be one value of f(x). As you see in the top left graph, there are two y values corresponding to the same x value.
712/8=?
First found out what 71/8 is. 71/8 is 8 and 7/8. This tells that there is 7 left so now you add 7 to two which gives you 72. Then you divide 72/8=9 and combine 8 and 9 which gives you 89. So 712/8=89
ANSWER
12
EXPLANATION
Two expressions for the angles in terms of x are given,
The first one is (10x-20)°
The second one is (6x+8)°
The two angles are angles on a straight line.
The sum of angles on a straight line is 180°.
This implies that,

Group similar terms,

Combine like terms:


Therefore the value of x is 12