I appreciate all who helps this is do in a few min. According to the Food and Drug Administration, the
recommended daily intake of iron is 18 mg. This is 4 less than twice
the recommended daily intake of zinc. What is the recommended
daily intake of zinc?

Greetings from Brasil...

Let's do

Fe = iron

Z = zinc

(remembering the periodic table)

According to the question of the statement:

Fe = 18

and

"... intake of iron is 18 This is 4 less than twice the recommended daily intake of zinc..."

That is, 18 of Fe is double that of zinc minus 4 units

Writing this situation mathematically:

Fe = 2 · Z - 4

18 = 2Z - 4

18 + 4 = 2Z

22 = 2Z

22/2 = Z

1 number

if we use a graphing calculator, there is only one such number that satisfies the conclusion of the mean value theorem, that is, a number such that

where the right-hand side is the average rate of change of f on the interval [0.5,0.75], which is the slope of the secant line.

in the attached graph, the black line is the secant line which has its slope as the average rate of change of f on [0.5,0.75], while the orange line is the only tangent line to the graph of f in the interval that satisfies the mvt conclusion.

i believe the answer is c.