In the first coil there are 5m of braid, and in the second one, 71 cm, how many centimeters of braid are in two coils.

Imagine that you are a salesperson and you need to calculate the length of the entire webbing in your two spools. To answer the question of the problem, you need to perform addition.
5 m + 71 cm = 5 m 71 cm = 571 cm
You can express 5 meters in centimeters, and then add
5 m = 500 cm
500 cm + 71 cm = 571 cm
Answer: 571 centimeters of tape in 2 spools.