Pls help! A farmer owns a total of 19 ducks and horses.
The ducks and horses have 64 legs altogether.
How many horses are there?

6 ducks and 13 horses

Step-by-step explanation:

Let H and D be the numbers of Horses and Ducks, respectively.

We are told that:

H + D = 19

Our biology book confirms that:

1 horse = 4 legs, and

1 duck = 2 legs

[In most cases on Earth]

So we can say that:

4H + 2D = 64 legs

Rewrite

H + D = 19 as:   H = 19 - D

and then substitute:

4H +2D = 64 legs

4(19-D) +2D = 64 legs

76 - 4D + 2D = 64 legs

-2D = - 12

D = 6  [We have 6 ducks]

Then:

H + D = 19

H + 6 = 19

H = 13  [There are 13 horses]

Check:

Do 6 ducks and 13 horses have a total of 64 legs?

6*2 + 4*13 = 64?

12 + 52 = 64?

YES

the weight of the object inside the box!

combine all like terms then its just a 2 step equation