Step1: Identify first transformation
The first step is a translation ($T$) that maps $\triangle ABC$ to $\triangle A'B'C'$, shifting the triangle vertically downward.
Notation: $T_{(0, k)}(\triangle ABC) = \triangle A'B'C'$ where $k<0$ (negative vertical shift)
Step2: Identify second transformation
The second step is a reflection ($r$) that maps $\triangle A'B'C'$ to $\triangle A''B''C''$, flipping the triangle over a vertical line (preserving orientation of vertices relative to each other, matching the shape change).
Notation: $r_{x=a}(\triangle A'B'C') = \triangle A''B''C''$ where $a$ is the vertical reflection line
Step3: Identify third transformation
The third step is a rotation ($R$) that maps $\triangle A''B''C''$ to $\triangle A'''B'''C'''$, rotating the triangle 90 degrees clockwise around point $A''$ (matching the final rotated position).
Notation: $R_{A'', -90^\circ}(\triangle A''B''C'') = \triangle A'''B'''C'''$