dennis spent double his weekly allowance to go to a concert. To earn more money his parents let him wash the car for $15. What is his weekly allowance if he ended with $2?

Answer 1

Let c = concert and a = allowance.

Here's what we know:

c = 2a (the concert costs twice his allowance)

15 - c = 2 (taking the concert ticket costs from the money he made washing the car leaves Dennis with only 2 dollars)

We have a value for c, so plug it in:

15 - 2a = 2

Isolate the a-value:

15 - 2a - 15 = 2 - 15

-2a = -13

-2a / -2 = -13 / -2

a = 6.5

Therefore, Dennis has a $6.50 allowance.

Answer 2

Solution:

Let the amount that Dennis spent be P dollars. Let the weekly allowance be A dollars

Then P = 2A , The amount that Dennis earned by washing the car is $15

His profit is $2

Use the following equation Profit = Amount Earned - Amount spent , then you can write:

$2 = $15 - 2A , solving for A , 2A = $15 - $2 = $13, A = $13/2 = $6.5 ( that is his weekly allowance)

Check in the equation $15 - 2($6.5) = $15-$13 = $2 checks