Answer:
79 centimeters
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