Question

Over a 9​-year period from 1990 to 1999​, the value of a baseball card increased by $18. Let x represent the number of years after 1990. Then the value​ (`y`) of the card is given by the equation `y=2x+47`?

Answer 1

original price is $47

Explanation:

I'm not exactly sure what it is you're trying to find, but I can try and help!

if x is the number of years after 1990, and its over a 9 year period, then x must be equal to 9. Let's plug it in.

`y=2x+47`
`y=2(9)+47`
`y=18+47`
`y=18+47`
`y=65`

this means that after 9 years, the value is $65. since we know that the value has increased by $18 since 1990, we can find the original value by subtracting

`65-18`
`47`

this means that the original value in 1990 is $47

(or `y=2x+47`
`y=2(0)+47`
`y=47`

Another way to find this is to look at the equation without doing any math.

using `y=2x+47`, we can tell that the annual increase (or slope) is two dollars every year. This is also in the word problem ($18 dollars every 9 years is $2/year.) If we know what the yearly increase is, we can tell that the last number (47) is the base price (the y-intercept).

This can also be graphed, which can help you find the price for any year

graph{2x+47 [-770, 747, -34.5, 157.6]}