14 - 2x = 4a - 16
First, add 2a to both sides. / Your problem should look like:
Second, simplify 4a - 16 + 2a to get 6a - 16. / Your problem should look like:
Third, add 16 to both sides. / Your problem should look like:
Fourth, add 14 + 16 to get 30. / Your problem should look like:
Fifth, divide both sides by 6. / Your problem should look like:
Sixth, 6 goes into 5 to get 30, so simplify

to 5. / Your problem should look like:
Seventh, switch your sides. / Your problem should look like:

Answer:
a = 5
This is what i did to get the answer.
225/ 4.5 = 50 seconds to finish the slushy.
6V + 2(V+12) = 488
8V = 464
V = 58 mph for 6 hours
V+12=70 mph for 2 hours.
check: 58*6 = 348
70*2 = 140
348 +140 =488
the car was traveling at 70 mph on the 2nd highway
Hope this helps?
Desmos is a great resource to help you understand the concept.
X + y = 4...x = 4 - y
2x + 3y = 0
2(4-y) + 3y = 0
8 - 2y + 3y = 0
-2y + 3y = 0 - 8
y = -8
x + y = 4
x - 8 = 4
x = 4 + 8
x = 12
solution is : (12,-8)