You know, if you check your calculator, it has a [ ₙPᵣ ] and also an [ ₙCᵣ ] button, and you could use that, now, if you want the factorial version,
Answer: 
Step-by-step explanation:
Move all terms to one side
Simplify
Split the second term
Factor out common terms in the first two terms, then in the last two terms.
Factor out the common term

Answer:
a=1/2
Step-by-step explanation:
From the question, the expression a(8x+7) is equivalent to 4x+3.5
Which means that multiplying 8x by a gives 4x and multiplying 7 by a gives 3.5
So, we can write the following to find the value of a

we can write the following
8ax=4x

Hence the value of a is 1/2
<h3>
Answer: 14s^4 - 7s^2 + 15</h3>
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Work Shown:
(12s^4-6s^2+4s)+(6s^4-4s+27)-(4s^4+s^2+12)
12s^4-6s^2+4s+6s^4-4s+27-4s^4-s^2-12
(12s^4+6s^4-4s^4)+(-6s^2-s^2)+(4s-4s)+(27-12)
14s^4-7s^2+0s+15
14s^4-7s^2+15
Note: don't forget to distribute the negative to every term in the last parenthesis