standard_description: Represent addition, subtraction, multiplication, and conjugation of complex numbers geometrically on the complex plane; use properties of this representation for computation. For example, (-1 + Ö3i)^(3) = 8 because (-1 + Ö3i) has modulus 2 and argument 120°.
problem_activity: Solve. Show or explain your work.
a.
$$\begin{align} 7,396 \\ {–\ 2,145}& \\ \hline \end{align}$$
b.
$$87,625-5,031=$$
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c.
$$\begin{array}{r} &19,850\\ -\!\!\!\!\!\!&15,761\\ \hline \end{array}$$


aligns: no