4. The recommended heart rate for weight management exercise and improving cardio fitness, in beats per minute, depends on a person's age
and can be represented by the expression 0.7(220 - a).

Part A: What does the variable in the expression represent?

Part B: Rewrite the expression using the distributive property.

Part C: what is the recommended heart rate for a 20-year-old person?

Part A: a=Age

Part B:

0.7 by 220

0.7 by a

then subtract the products

Part C: 140bpm

1.4

2.3

step-by-step explanation:

the formula for the constant of variation is

y= kx

divide each side by x

y/x =kx/x

y/x =k

we know a and y

1.   y/x = k

4/1 =4

check the other values to make sure they are the same

8/2 = 4   12/3 =4   and 16/4 =4  

the constant of variation is 4

2.   y/x = k

3/1 =3

check the other values to make sure they are the same

6/2 = 3   9/3 =3   and 12/4 =3  

the constant of variation is 3

the balance is found at the link

step-by-step explanation: