Terry is mailing two boxes. Together they weigh 21 lbs. If the smaller box is 5 lbs. less than the larger one, how much does each box weigh? Write and solve an equation that models this scenario.

x+y=21

x = y-5

y-5+y=21
...

To solve this problem, we can represent the weight of the larger box as "x" and the weight of the smaller box as "x - 5".

According to the problem, the total weight of the two boxes is 21 lbs, so we can set up the equation:

x + (x - 5) = 21

We combine the like terms:

2x - 5 = 21

Now, we want to isolate the variable "x", so we add 5 to both sides of the equation:

2x - 5 + 5 = 21 + 5

2x = 26

To solve for x, we divide both sides of the equation by 2:

2x/2 = 26/2

x = 13

So, the larger box weighs 13 lbs, and the smaller box weighs 13 - 5 = 8 lbs.