If you bought a cookie for 80¢ and paid for it with a 5 dollar bill, how much change would you receive?

$4.20

Step-by-step explanation:

What you bought will be subtracted from how much you paid with.

amount paid - amount bought

We paid for the cookie with $5, and bought something for 80 cents.

$5 is equal to 5.00, and 80 cents is equal to 0.8

5.00-0.8=4.2

So, you would get $4.20 back in change

x = 25,

y = 10

Step-by-step explanation:

Call the larger number "x", and the smaller one "y".

Set up a system, based on the given infomration

x + y = 35

x - y = 15

Solve the system by elimination, in this case, one can just add the two systems to eliminate a variable.

x + y = 35

x - y = 15

x + y + x - y = 15 + 35

Simplify,

2x = 50

Inverse operations,

2x = 50

/2     /2

x = 25

Substitute back in to find y,

x + y = 35

x = 25

25 + y = 35

Inverse operations,

25 + y = 35

-25         -25

y = 10