can someone help with this math puzzle?

[dancing in the rain<3]

Each letter in this puzzle stands for a # 1-9. No two letters stand for the same digit, one letter represents the same digit throughout the puzzle. Make the statements true.
Puzzle:
K+E+E+P= 11
C+O+R+D= 30
F+O+O+D= 28
R+E+A+R= 15
R+O+C+K= 24

can any help me? i dont even know where to start on here.

 

[ernie]

1+2+3+5=11
6+8+7+9=30
9+8+8+3=28
3+7+3+2=15
4+8+3+9=24
Hope this is the right idea, not done a math puzzle f years!

 

[Peter Pan's Lost Girl]

Ok I got close...

9+8+6+7
(CORD)

5+8+8+7
(FOOD)

1+4+4+2
(KEEP)

6+8+9+1
(ROCK)

6+4+3+6
REAR)?????


I was so close

 

[Bebop (the evil hamster)]

someone tricked you into solving a system of equations huh?

 

[b_remer]

star by solving for one letter, I suggest O because its involed in the most eqautions. If you don't know what I mean by this..well your in trouble. Just trying to get you started