Question

Write a system of equations to describe the situation below, solve using any method, and fill in the blanks.

Answer 1

Answer:

A dozen chocolate cookies cost $6

and a dozen oatmeal cookies cost $7

Step-by-step explanation:

Let cost of 1 dozen chocolate cookies = x

Let cost of 1 dozen oatmeal cookies = y

then we get equations:

9x+8y=110...(i),

and 9x+5y=89...(ii)

Solve equation (i) for x

9x+8y=110

9x=110-8y

$x=\frac{110-8y}{9}$...(iii)

plug (iii) into (ii)

9x+5y=89

$9\left(\frac{110-8y}{9}\right)+5y=89$

$110-8y+5y=89$

$9\left(\frac{110-8y}{9}\right)+5y=89$

$110-3y=89$

$-3y=89-110$

$-3y=-21$

$y=7$

plug y=7 into (iii)

$x=\frac{110-8y}{9}=\frac{110-8(7)}{9}=6$

Hence final answer is given by:

A dozen chocolate cookies cost $6

and a dozen oatmeal cookies cost $7