Answer
The units ordered from suppliers in Toronto, Montreal, and Ottawa are $22,56,22$ respectively.
Work Step by Step
1. Assume the units ordered from suppliers in Toronto, Montreal, and Ottawa are $x,y,z$
2. Based on the given conditions, we have: $\begin{cases} x+y+z=100 \\ 80x+50y+65z=5990 \\ x=z \end{cases}$
3. Use the third equation in the other two, we have $\begin{cases} 2x+y=100 \\ 145x+50y=5990 \end{cases}$
4. Multiply -50 to the first equation to get $-100x-50y=-5000$, then add it to the second equation, we have $45x=990$, thus $x=22$
5. We have $y=100-2x=56$ and $z=x=22$
6. The units ordered from suppliers in Toronto, Montreal, and Ottawa are $22,56,22$ respectively.
