Step-by-step explanation:
3 is cross multiplication
2 is proportion
and 1 is equal
He brought 6 math books and 6 science books
Answer:
B : -2
Step-by-step explanation:

Answer:
618 birds.
Step-by-step explanation:
Let the estimated number of birds=x
Out of x birds, he tied a belt around the legs of 40 birds.
When he observed 520 birds, 34 of which had belts.
Expressing each as a ratio

Cross Multiply
34x=520X40
x=520X40÷34=611.7≈618
There are an estimated 618 birds.