story problem help

Question

Mom and Maria work a deal. Every day that Maria walks dog she gets $1.00. For every day she doesn't walk dog she gives $1.00 back to her Mom. Maria makes a total of $19.00 during the month of march. How many days did Maria walk the dog in March?

Answer 1

let x be the days walk the dog

let y be the days without walking the dog

 

since March ha 31 days:

 

x + y = 31              eq. 1

 

x - y = 19               eq. 2

 

use eq. 2 to solve for x:

 

x = 19 + y              eq. 3

 

substitute eq. 3 into eq. 1:

 

(19 + y) + y = 31

 

19 + 2y = 31

 

2y = 12

 

y = 6

 

so,

 

31 - 6 = 25

 

so dog was walked 25 days in March