Two sides of a triangle are 9 cm and 12 cm long. what is the range of possible lengths for the third side?
select one:
a. 2 cm < x < 24 cm
b. 2 cm < x < 21 cm
c. 2 cm < x < 18 cm
d. 3 cm < x < 21 cm
e. 3 cm < x < 18 cm
f. 6 cm < x < 24 cm
g. 6 cm < x < 21 cm

Step-by-step explanation:

According to geometry, the third side cannot be grater than the sum of two given sides, and cannot be less than the difference of those sides. So, we have:

9+12=21cm

12-9=3 cm

So, the third side has to be less than 21cm and more than 3 cm.

Therefore, the answer is d.

Step-by-step explanation: