Convert the denominator of the first two fractions to 24 since 3 and 8 can fit into 24.
3/8=9/24
2/3=16/24
Now add them together.
9/24+16/24=25/24
Next add the second two fractions 9/24 and 16/24.
9/24+16/24=25/24
Since all fractions equal 25/24, the equation was true!
Hope this helps!
The Jacobian for this transformation is

with determinant
, hence the area element becomes

Then the integral becomes

where
is the unit circle,

so that

Now you could evaluate the integral as-is, but it's really much easier to do if we convert to polar coordinates.

Then

I ounce is 2 tablespoons so do 12 times 2 and that is 24 then multiply 3.99 times 2 thats your answer 7.98
Let's simplify step-by-step.
<span><span><span><span>2b</span>+<span>3r</span></span>+<span>4b</span></span>+r</span>
Combine Like Terms:
<span>=<span><span><span><span>2b</span>+<span>3r</span></span>+<span>4b</span></span>+r
</span></span><span>=<span><span>(<span><span>2b</span>+<span>4b</span></span>)</span>+<span>(<span><span>3r</span>+r</span>)
</span></span></span><span>=<span><span>6b</span>+<span>4r</span></span></span>
Answer:<span>=<span><span>6b</span>+<span>4<span>r</span></span></span></span>