Ineed with my system of equations in algebra ill give one example i have:
y=-x-2
-9=2x+3y
i am sort of confused and just need some understanding how to do it !

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

He weights of 2-pound bags of best dog food are approximately normally distributed with a given mean  and standard deviation  according to the empirical rule, what percentage of the bags will have weights within 3 standard deviations of the mean? 47.5%68%95%99.7%

What is the value for this expression? 2e-5