Answer:

There were 12 lambs in the farm

Step-by-step explanation:

Let D = ducks , and L = lambs

Now , given that the total is 20 so

• D + L = 20

Then , if there were 64 legs altogether. Remember that Ducks only have 2 legs and lambs have 4 legs.

• 2D + 4L = 64

Solving the system of linear equation: By substitution:

D + L = 20

D = 20 - L

» Substitute the value of D to the other equation

2D + 4L = 64

2(20-L) + 4L = 64

40-2L + 4L = 64

40 + 2L = 64

2L = 64-40

2L = 24

L = 12