What is the constant of proportionality?

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.

Anyone know? is appreciated! will mark brainliest if correct!

Which expression is equivalent to 8(k + m) − 15(2k + 5m)?