Shanice and jenny each improved their yards by planting grass sod and ornamental grass. they bought their supplies from the same store. shanice spent $280 on 14 feet of grass sod and 14 bunches of ornamental grass. jenny spent $251 on 12 ft of grass sod and 13 bunches of ornamental grass find the cost of one ft of grass sod and the cost of one bunch of ornamental grass.

Grass sod: $9

Ornamental grass: $11

Explanation:

In order to solve this we first have to set a term for each Grass sod and ornamental grass, we will use X and Y for each one:

Grass sod: X

Ornamental grass: Y

So we create two equations:

14x + 14y=280

12x+13y=251

We can solve this system of ecuations by elimination:

Now we just inser the value of Y into anyone of the two equations:

So we know that the grass rod costs 9 dollars and the ornamental grass 11

it is b that is the answer.

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol