Answer
a. $\{ -13, -\frac{12}{4}=-3, 0, \sqrt {49}=7 \}$
b. $\{ -13, -\frac{12}{4}=-3, 0, \frac{3}{5}, 5.9, \sqrt {49}=7 \}$
c. all numbers.
Work Step by Step
Given $A=\{ -13, -\frac{12}{4}=-3, 0, \frac{3}{5}, \frac{\pi}{4},5.9, \sqrt {49}=7 \}$, we have:
a. Integers are $\{ -13, -\frac{12}{4}=-3, 0, \sqrt {49}=7 \}$
b. Rational numbers are $\{ -13, -\frac{12}{4}=-3, 0, \frac{3}{5}, 5.9, \sqrt {49}=7 \}$
c. Real numbers are all numbers in the list.
