Answer:

Step-by-step explanation:
The complete question in the attached figure
we know that
The <u><em>Triangle Exterior Angle Theorem</em></u> states that: An exterior angle of a triangle is equal to the sum of the opposite interior angles.
In this problem

solve for x


<span>his average speed is </span>12 2/3 kilometers per hour
(a+a+6)*2.5=345
2a+6=138
a=132/2
a=66 mph
a+6=66+6=72 mph
Speed of the first car is 72 mph
F^1(-2) = 2(-2) = -4
f(-4) = 1/2 * -4 = -2
f(f^-1(x)) = x so answer is -2