believe the answer is A. 7(6+2)
Answer:
2.69 x 
Step-by-step explanation:
We are given the heart's speed - 70 bpm
We count the number of minutes in 73 years :
- 1 year = 365 days
- 1 day = 24 hours
- 1 hour = 60 minutes
- 73 x 365 x 24 x 60 = 38,368,800 minutes
We multiply the heart's bpm with 73 years worth of minutes
38,368,800 x 70 = 2,685,816,000
Write the number in scientific notation = 2.68581 x
≈ 2.69 x 
The r% of a quantity x is computed by dividing x in 100 parts, and considering r of such parts. So, the r% of the male is

and similarly, the r% of female is

The number of males decreased by this quantity, so now it is

and the number of female increased by this quantity, so now it is

we know that these two new counts are the same number, so we can build and solve the equality

Subtract 20 and add 0.3r from both sides:

Divide both sides by 0.5 to solve for r:

Let's check the answer
The 20% of 30 is
, while the 20% of 20 is 4. So, we are stating that
which is true because both expressions evaluate to 24.