In the metric system of units:1 meter=100 centimeters and 1 meter:1 foot=3.25:1

As the question is incomplete, the complete question is;

How many meters are there in 21 feet? Note: In the metric system of units: 1 meter = 100 centimeters and 1 meter:1 foot = 3.25:1

The ratio of 1 meter to 1 foot is given that is 3.25:1

meter : foot

3.25 : 1

when there is 21 foot, it means multiply both sides of ratio with 21

3.25 x 21 : 1 x 21

68.25 : 21

Thus, if there is 21 foot, it means it is equal to 68.25 meters.

And if convert meter to centimeter;

68.25m = 68.25 x 100 cm

= 6825 cm