the cost of ketchup is $3.53 & mustard is $0.63 .
<u>Step-by-step explanation:</u>
Here we have , Brianna bought 3 bottles of ketchup and 2 bottles of mustard for $11.85. Logan bought 3 bottles of ketchup and 5 bottles of mustard for $13.73. We need to find the cost of each. Let's find out :
Let cost of ketchup be x and mustard be y than ,
Brianna bought 3 bottles of ketchup and 2 bottles of mustard for $11.85
We have following equation ,
⇒
..........(1)
Logan bought 3 bottles of ketchup and 5 bottles of mustard for $13.73
We have following equation ,
⇒
........(2)
Now , (2) - (1) , i.e.
⇒ 
⇒ 
⇒ 
Putting value of y in (1) :
⇒ 
⇒ 
⇒ 
Therefore , the cost of ketchup is $3.53 & mustard is $0.63 .