6a-4 = 3a+54
3a = 58
a = 58/3
a= 19.333
Answer: There are 99 three-legged-cows and 28 chickens.
Step-by-step explanation:
Let x be the number of three-legged-cows and y be the number of chickens.
Number of legs in chicken = 2
The according to the question, we have the following equations :-

Multiplying 2 to the equation (1), we get

Now, subtract equation (3) from (2), we get

Put x= 99 in (1), we get

Hence, there are 99 three-legged-cows and 28 chickens.
This equation says that 6 = 4, which is incorrect. However, if there was no - 2 on the right side of the equation the answer would be correct as 6 = 6
12) (shaded region) 12x25 =300
( un- shaded region) 6x10=60
300-60=240
240 is the answer for #12