Acute: anything less than 90 but greater than 0
so, m<CAD
right: angles at exactly 90 degrees, so m<AEC,
and obtuse angles are anything greater than 90 but less than 180 degrees,
so CDA (you can tell by the picture that it is bigger than 90- 90 degrees is exactly perpendicular)
For this case we have the following equation:

The variables are:
t: time in hours
d (t): distance traveled in miles.
We evaluate the distance traveled after 4 hours.
So we have that for t = 4:
Answer:
d (4) = 68
This means that after 4 hours Joanna cycled for 68 miles total
Use the difference of squares factorization - that for any numbers a and b, (a-b)(a+b)=a^2-b^2.
We have:
(x^2+1)(x^2-1)=x^4-1
In addition:
(x-1)(x+1)=x^2-1, so we have:
(x^2+1)(x+1)(x-1)
As our complete factorization.
Answer:
a = -27
d = -21 - ( -27) => 6
a62 => a + 61 (d) +=> -27 + 61(6)
=> -27 + 366
=> 339