A dog buried 18 bones in his backyard. On Monday, he dug up 1/2 of his bones. On Tuesday, he dug up another 1/3 of his bones. How many bones are still buried?

3

Step-by-step explanation:

A dog buried 18 bones

On Monday he dug up 1/2 of the bones

On Tuesday he dug up 1/3 of the bones

= 1/2 × 18

= 9

= 1/3×18

= 6

Therefore the remaining bones still buried in the ground can be calculated as follows

= 9+6

= 15

= 18-15

= 3

Hence 3 bones are still buried in the ground

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225

a. is correct