1) you first need to find a couple equations so you can solve the system:

L = 6 + 2W

Perimeter = 48 = 2W + 2L

Then you can solve the system:

L = 6 + 48 - 2L

3L = 54

L = 18

Then you can plug L back into the second equation and find W:

48 = 2W + 2(18)

2W = 12

W = 6

So the solution is:

L = 18

W = 6

2) This looks like a physics formula for kinetic energy, but since you have the numbers it's just an algebra problem.

K = 1/2 *mv^2

460 = 0.5*m*(5.0)^2

Simplify:

460 =0.5*m*25

460 = 12.5*m

Solve:

m = 36.8

Are there any specific issues you're having with the concepts?