a. The first variable is x and the second variable is y.
b. The equations are 
and 
Step-by-step explanation:
Step 1:
The first step is to define the variables. The variables can be any two symbols, letters, characters, etc.
Here let the first variable be x and the let the second variable be y.
So the variables are defined as x and y.
Step 2:
The sum of the given variables is 12.
The first variable + the second variable = 12,
The difference between the two variables is 4.
The first variable - the second variable = 4.
Step 3:
If we add both the equations we get, 
and 
x = 8 and y = 4.
I’m pretty sure it would be a and b
Hey I don't know who Mhanifa is but 25 is correct, and I will put the entire explanation to how to get the answer here.
First of all the 2 lines on the left and right side of the triangles are means that those 2 lines are equal and thus forming a isosceles triangle.
This means that the bottom right angle is also 2x+2 degrees.
Now because all 3 angles in a triangle adds to 180 degrees, we can set up equation.
3x+1+2x+2+2x+2=180
Now combine like terms
7x+5=180
Then solve, first subtract 5 from both sides.
7x=175
Now divide 7 from both sides
x=25
Let distance be s and velocity be v
s = 5t⁴ - 10t² + 6
We know velocity is the change in distance per unit time, so
v = ds/dt
v = 20t³ - 20t
144 miles on 4.5 gallons
Solution: 144mi 4.5 32mi
------------ divided by = -------------
4.5gal 4.5 1 gal
