When you add a zero to the problem, it shows you are now multiplying in the double-digits. Let's say you are multiplying 12x12. First you cover up the one then multiply them. Then cover up the two and you have 10. When you multiply them, it ends in a zero. Don't think of it as adding a zero but adding to products.
Answer:

Step-by-step explanation:
We have the equation 
In order to solve for x, we need to get all of the x's to one side and everything else to the opposite side

First, we can add 1 to each side

Now, we can add x to each side

Next, we can divide each side by 2

And here is our answer.
7% of $5100 is 357
416.50 / 357 = 1.16
I will take 1.16 years to gain $416.50
Answer:
9 yards
Step-by-step explanation:
36 divided by 4 = 9
Answer:
84 feet to the nearest foot.
Step-by-step explanation:
We have a right angled triangle with adjacent side (A) = 100 and you want to find the height of the tower, the opposite side (O).
A = 100 , O = ? so we need the tangent , (from SOH-CAH-TOA).
tan 40 = O/ 100
O = 100 tan 40
= 83.9 feet.