She has 5 ounces of toppings.
The reasoning is you first do 5-2.75 because you must subtract the basic sandwich from the total cost. Then, you must divided 2.25/0.45 because that is the cost of the remaining toppings.
All others did not satisfy the inequality simultaneously except #4 and #6
For #4:
2 < 5(1) + 2 i.e. 2 < 7 (true)
2 >= 1/2(1) + 1 i.e. 2 >= 3/2 (true)
For #6
2 < 5(2) + 2 i.e. 2 < 12 (true)
2 >= 1/2(2) + 1 i.e. 2 >= 2
That just means that you are dividing by -3 so when you do 45 divided by -3 what do you get?
1. Denote by

the region bounded by the cylinder

and the planes

and

. Converting to cylindrical coordinates involves setting

and

is obtained by varying the parameters over

,

, and

. The volume element is

so the integral becomes

2. Now let

denote the region bounded by the sphere

and the coordinate planes in the octant in which each coordinate of the point

is negative.
Converting to spherical coordinates, we set

where we obtain

by varying over

,

, and

. The volume element is now

so the integral becomes