Not too sure what you're asking, but...
3(x+2) is the expression
16 - (-15) = 16 + 15 = 31...difference of 31 degrees
All exercises involve the same concept, so I'll show you how to do the first, then you can apply the exact same logic to all the others.
The first thing you need to know is that, when a certain quantity multiplies a parenthesis, you can distribute that number to every element in the parenthesis. This means that

So,
is multiplying the parenthesis involving
and
, and we distributed it:
multiplies both
and
in the final result.
Secondly, you have to know how to recognize like terms, because they are the only terms you can sum. Two terms can be summed if they have the same literal expression. So, for example, you cannot sum
, and neither
exponents count.
But you can su, for example,

or

So, take for example exercise 9:

We distribute the 1.2 through the first parenthesis:

And you can distribute the negative sign through the second parenthesis (it counts as a -1 to distribute):

So, the expression becomes

Now sum like terms:

Two equations with infinite solutions would look the exact same. Example:
y=mx+b
y=mx+b
Example 2
y=2x+5
y=2x+5
For an equation with no solution they would have the same slope but different y intercepts. An equation with same slope and same y intercepts would have infinite solutions.
Answer:
(f+g)(x) = x^3 - 3x + 2
Step-by-step explanation:
Find (f+g)(x) by adding together f(x) = -3x + 2 and g(x) = x^3:
(f+g)(x) = -3x + 2 + x^3, or, in standard form,
(f+g)(x) = x^3 - 3x + 2