Answer:
75
Step-by-step explanation:
Substitute 6 for f
12f+3=
12*6+3=
72 + 3 = 75
Melanie: 15 years old
Kevin: 5 years old
Assume Kevin's present age is x.
That means that 3 years ago, his age would be x - 3.
Melanie's age would be 6(x - 3).
Same thing for 5 years into the future:
Kevin's age would be x + 5.
Melanie's age would be 2(x + 5).
The two equations we have here are:

By subtracting both equations, we are simplified to:
8 = -4x + 28
By solving the equation, we get x = 5.
That means that Kevin's current age is 5 years old.
Melanie's age could be calculated by substituting Kevins'.
6(x - 3) --> 6(5 - 3) --> 12
Since that was 3 years ago, you need to add 3 to 12 to get her current age.
12 + 3 = 15
Melanie's current age is 15 years old.
Answer:
They will meet in 1.8 hours.
Step-by-step explanation:
Given that, distance between trains = 306 miles
Let they take time
to meet each other.
Speed of first train = 90 mph
Speed of second train = 80 mph
Let distance traveled by first train =
miles
Formula for distance:

Distance traveled by first train, 
Let distance traveled by first train =
miles
Formula for distance:

Distance traveled by first train, 
Total distance traveled is 306 miles.
i.e.

They will meet in 1.8 hours.
Answer:
20x + 26
Step-by-step explanation:
Rewrite the equation to make distributing easier:
7(2 + 2x) + (x + 2) x 6
7(2 + 2x) + 6(x + 2)
Distribute the 7 and 6 to each set of parentheses:
14 + 14x + 6x + 12
Add like terms:
20x + 26
So, the equivalent expression is 20x + 26