Subtract 4x^3-6x^2+8x-9 from 7x^3-16+18

What are potential hypotheses (explanations) regarding why there are ecological equivalents between many metatherians and eutherians? discuss your hypothesis in terms of the processes that could lead to the current ecologies and distributions of metatherians and eutherians.

Solve this riddle: i am an odd number. i an less than 100. the some of my digit is 12. i am a multiple of 15. what number am i?

What is the sum of these mixed numbers 4 2/3+ 3 1/9