A plant is 58 centimeters tall, and it grows one centimeter each month.

How tall is it after 21 months.

79 centimeters

Step-by-step explanation:

Identify what you know:

1) The plant is 51 centimeters tall

2) The plant grows 1 cm more each month

So, we can create a formula to find the answer, where x equals the number of months after the plant was 58 cm tall.

58 + (1 times x) = height of plant

58 + (1 x 21) = ?

58 + 21 = ?

? = 79 cm

This means that after 21 months, the plant would have grown 21 centimeters more (because 1 cm every month, 21 months, 1 * 21 = 21). Add them:

58 + 21 = 79 centimeters.