I confused ! I don't get what your trying to say please explain better !
Given number is 4,8100,000,000,000.
In this number of zero is 11. So we can write it as

But for scientific notation we will enter decimal after two place in reverse direction.For this we will also multiply number by 10^2.
So number will be

So fourth option is correct.
A/3=7/10
21=10a
a=2.1
100a=100*2.1=210
The denominator of the second fraction can be factored as (a-2)(2a-7), then it becomes doable. You cancel the (2a-7) factors, and are left with:

Do note that you have erased the fact that a≠0 and a≠7/2, so you should always mention that.
To answer this question you will need to know how many inches the car travels Per minute.
1. To find this out you will first divide 45 miles by 60 to get the number of miles per minute.
The convertible travels 0.75 mi./min.
2. Next you will convert this number of miles to inches.
There are 63,360 inches per mile.
0.75 x 63360 = 47520 inches per minute.
3. You then need to find the distance the wheel travels in one rotation. You will need to find the circumference of the wheel.
C = pi x d
3.14 x 48
C = 150.72 inches
Each rotation is about 150.72 inches.
4. Finally, divide the total distance traveled in a minute by the circumference(distance of one rotation) to get the total number of rotations in a minute.
47520/150.72 is about 315.3 rotations per minute.