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?

22.

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm