Answer:
A. x = 3 units
B. r = 6 units
Step-by-step explanation:
A. The length of the whole tightrope is 12 units. It is divided into 4 equal parts, each of length x units.
So,
[tex]4x=12\\ \\x=3\ units[/tex]
B. The length of the whole tightrope is [tex]21+r[/tex] units. It is divided into 5 parts. Four of them are equal and each has the length of r units and the fifth part has the length 3 units.
So,
[tex]4r+3=21+r[/tex]
Subtract r:
[tex]4r+3-r=21+r-r\\ \\3r+3=21[/tex]
Subtract 3:
[tex]3r+3-3=21-3\\ \\3r=18\\ \\r=6 \ units[/tex]