Answer:

Step-by-step explanation:
Hello,
let's find a and b reals so that


we identify the terms in 
9 = 3a
we identify the terms in x
-18 = 3b + a
we identify the constant terms
-7 = b
so ti goes with a = 9/3 = 3, b = -7
so we can write

so 
hope this helps
Speed = distance over time.
300/5 is the same as 300÷5, which is 60
Answer:
12
Step-by-step explanation:
since DE and EF are congruent then we now know that EF is also 12
Answer: D) 155
Step-by-step explanation:
let <A, <B,<C are three angles in a triangle.
sum of the three angles in a triangle is 180degree.
<A+<B+<C=180
130+<B+<C=180 since one angle is given
<B+<C =180-130
<B+<C=50
(<B+<C)/2=25----(1)after bisecting sum of the angles
required angle =180-25=155
d is correct answer
Combinatorial Enumeration. That whole class was a rollercoaster ride of mind-blowing generating functions to prove crazy things. The exam had ridiculous questions like 'count the number of cactus trees with n vertices such that etc etc etc' and you'd do three pages of terrible terrible sums and algebra. Then your final answer would be something beautiful like n/2 and you'd breath a sigh of relief and thank the math gods.