## Precalculus (6th Edition)

$\{(-1,3)\}$
1. Express y from the first equation (solve for y) $7x-y=-10\qquad/+y-10$ $7x-10=y$ $y=7x+10$ 2. Substitute y in the other equation and solve. $3(7x+10)-x=10$ $21x+30-x=10\qquad/-30$ $20x=-20\qquad/\div 20$ $x=-1$ 3. Back-substitute into the expression of y (step 1). $y=7(-1)+10=3$ 4. Write the solution as an ordered pair. Solution set: $\{(-1,3)\}$