A landscaping business bought 8 rose bushes and 15 daylilies for $193. They went back later and bought 3 more rose bushes and 12 daylilies for $117. How much does each daylily cost?

Each daylilies  cost $7

Step-by-step explanation:

Step one:

let roses be x

and daylilies be y

so

8x+15y=1931

also

3x+12y=1172

we can solve equations 1 and 2 by substitution

8x=193-15y

x=(193-15y)/8

put x= (193-15y)/8  in 3x+12y=117

3((193-15y)/8)+12y=117

(579-45y)/8+12y=117

579-45y=8(117-12y)

579-45y=936-96y

collect like terms

579-936=-96y+45y

-357=-51y

divide both sides by -51

y=-357/-51

y=7

Hence each daylilies  cost $7

put y=7 in eqn 1

8x+15(7)=193

8x+105=193

8x=193-105

8x=88

x=88/8

x=11

rose cost $8

b.) 160 miles on a 5 gallons car

step-by-step explanation:

240/10=24 miles/gallon

160/5=32 miles/gallon

30/1=30 miles/gallon

168/6= 28 miles/gallon

32 miles/gallon is the most amount, so this is the best.

distance covered by pamela in 9 l of fuel = 99km

let us apply unitary method here.

distance covered by pamela in 1 l of fuel =99/9 =11 km

now let us find distance covered by pamela if she has 12 l of fuel.

distance covered in 12 l = distance covered in 1 l of fuel * 12

we know that distance covered by here in 1 l is 11 km.

so distance covered in 12 l of fuel = 11*12 = 132 km.