Answer:
a=9
Step-by-step explanation:
To solve this proportion, we have to get the variable, a, by itself.
First, cross multiply.
6/a=18/27
Multiply the denominator of the first fraction by the numerator of the second, and the numerator of the second by the denominator of the first.
a*18=6*27
18a=162
Now, 18 and a are being multiplied. In order to get a by itself, perform the opposite of what is being done. They are being multiplied, so the opposite would be division. Divide both sides by 18.
18a/18=162/18
a=162/18
a=9
So, the proportion, with 9 substituted in for a, will be:
6/9=18/27
The answers are (-3,-12), (-2,-10), (5,4)
In the 
direction we consider the 
subintervals [0, 1] and [1, 2] (each with length 1), while in the 
direction we consider the 
subintervals [0, 2] and [2, 4] (with length 2). Then the lower right corners of the cells in the partition of 
are (1, 0), (2, 0), (1, 2), (2, 2).
Let 
. The volume of the solid is approximately
###
More generally, the lower-right-corner Riemann sum over 
and 
subintervals would be
Then taking the limits as 
and 
leaves us with an exact volume of 
.
