Answer
The number is $-5$.
Work Step by Step
Let $x$ be the unknown number.
Then thrice the number is $3x$.
Translating $``\text{difference between three times a number and 4}"$ yields $3x-4$.
Thus, the equation needed to find the unknown number is:
$$3x-4=-19$$
Solve the equation:
$$\begin{align*}
3x-4+4&=-19+4 &\text{Add 4 to both sides.}\\
3x&=-15 &\text{Simplify.}\\
\frac{3x}{3}&=\frac{-15}{3} &\text{Divide 3 to both sides.}\\
x&=-5 &\text{Simplify.}
\end{align*}$$
Thus, the number is $-5$.
