Like terms are terms whose variables are the same. In this case, 7 and 2 have no coefficients therefore are like terms. For example, 7x and 2x would both be like terms because they have the same coefficient which is x.
So, here we have an exponential function.
Remember that an exponential function has the form:

Where a represents an initial amount, and r is the rate of this amount to change. (Increase, or decrease).
So, given that the population of City A in 2000 was 40 thousand people and the population increased by 13% each year, we can say that

So,

For city B:

But something different happens with city C. This is not an exponential function, this is a linear function.
So,

The best answer I can think of is that a line doesn't have a point where it starts or stops, but instead goes on forever, unlike a ray which has a start or end point but not the other, and a line segment which has a start and stop point. Hope this helps!
Answer:
23
Step-by-step explanation:
This equation can be derived from the question
let a represent the initial number Gus started with
{[(a x 8) - 12] / 4 } + 7 = 50
subtract 7 from both sides of the equation
[(a x 8) - 12] / 4 } = 43
Multiply both sides of the equation by 4
(a x 8) - 12] = 172
Add 12 to both sides
8a =184
Divide both sides by 8
a = 23.