Question

Jay can buy a stereo either online or at the local store. If he buys online he gets a 15% discount, but has to pay a $12 shipping fee. At the local store, The stereo is not on sale, but there is no shipping fee. For what regular price is it cheaper for J to buy the stereo online

Answer 1

15% discount means u r paying 85% for it
x = original price

0.85x + 12 < x
12 < x - 0.85x
12 < 0.15x
12/0.15 < x
80 < x.....so for it to be cheaper online, it would have to cost more then 80....so 81 or higher

Answer 2

Let

x------> the regular price of the stereo in dollars

we know that

If Jay buy a stereo online

He has to pay

`x(1-0.15)+\$12=0.85x+\$12`

If Jay buy a stereo at the local store

He has to pay

`x`

Is cheaper for Jay to buy the stereo online when

`0.85x+\$12 < x\\0 .85x-x < -12\\- 0.15x < -12\\ 0.15x > 12\\ x > 12/0.15\\ x > \$80`

therefore

the answer is

The regular price must be greater than
`\$80` for Jay to buy the stereo on line