C,D and F are correct.
C is what you would think of when reading it, you walked 12 and walked 1/4(12) more.
12 + 12(1/4) =
12 + 3 =
15
D is equal to C when simplified,
12(1+1/4) =
12 + 3 =
15
F is the same as the D, it just simplified the numbers in the parenthesis
12(1+1/4) =
12(4/4 + 1/4) =
12(5/4) =
15
2 groups if 4 bicyclists or 4 groups of 2 bicyclists. Well it's only 1.75 per truck so since there were 4 trucks 4•1.75=7.00 :)
The answer to you question is c
Lia=L
Phil=12.80+L
Cam=3L
L+12.80+L+3L=200.30
5L+12.80=200.30
5L=200.30-12.80
5L=187.5
L=187.5/5
Plug into the equations at the top
L=Lia=$37.5
Phil=12.80+37.5=$50.30
Cam=3(37.5)=$112.50