This is a word problem signifying an algebraic expression.
Translating this to mathematics:

add 4 to both sides.
divide 16 to both sides.
this is:
Answer:
21
Step-by-step explanation:
Answer:
multiply it by zero
Step-by-step explanation:
zero times anything is zero
<span>The work surface should be between 20 and 30 inches deep and at least 24 inches wide. For maximum flexibility, the height should be that of a conventional writing desk, about 28 to 30 inches, with the keyboard resting on an adjustable shelf. Seat height should be adjustable from 16 to 20 inches</span>
Answer:
B
Step-by-step explanation:
A graph is only a function when there is only one y value for each x value.
A trick is to draw a line through some points on the x-axis, and if the line goes through more than one point. Then it is not a function. (See picture)
Sorry, not all the lines are straight, but you get the point. B is the only one that doesn't have more than one point on the lines I drew.