A worker has at most $20$ hours and must earn at least $180$ at $\$12x$ and $\$9y$. Which system models this?

$x + y \le 20,\ 12x + 9y \ge 180$

When solving a system by elimination, why can you add a multiple of one equation to another?

It produces an equivalent system with the same solutions

12questions. Pick an answer and you'll see why right away.

What is the solution to $\begin{cases} y = x + 1 \\ 2x + y = 10 \end{cases}$ ?
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A worker has at most $20$ hours and must earn at least $180$ at $\$ 12x $and$ \ $9y$ . Which system models this?
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A line and a parabola can intersect at most how many times?
When solving a system by elimination, why can you add a multiple of one equation to another?