Question 23
Integers $a,$ $b,$ and $c$ satisfy
$$
\begin{aligned} ab + c &= 100, \\ bc + a &= 87, \\ ca + b &= 60. \end{aligned}
$$
What is $ab + bc + ca?$
$$
\begin{aligned} ab + c &= 100, \\ bc + a &= 87, \\ ca + b &= 60. \end{aligned}
$$
What is $ab + bc + ca?$