20.37154878746336 rounded to the nearest whole number

The answer is 20, because in the 3 in the tenths place is not greater than 5, therefore not allowing 20 to go up to 21. All the other numbers are not needed since you are only rounding to the nearest whole number.

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.