Question

Y=x+3 and y=3x+6 system of substitution

Answer 1

`\left\{\begin{array}{ccc}y=x+3&(*)\\y=3x+6&(**)\end{array}\right\\\\\text{Substitute}\ (*)\ \text{to}\ (**):\\\\x+3=3x+6\qquad\text{subtract 3 from both sides}\\\\x=3x+3\qquad\text{subtract 3x from both sides}\\\\-2x=3\qquad\text{divide both sides by (-2)}\\\\\boxed{x=-1.5}\\\\\text{Put the value of x to}\ (*)\\\\y=-1.5+3\\\\\boxed{y=1.5}\\\\Answer:\ \boxed{x=-1.5\ and\ y=1.5\to(-1.5;\ 1.5)}`

Answer 2

`\left \{ {{y=x+3} \atop {y=3x+6}} \right. \\\\ \left \{ {{y=x+3} \atop {3x+6=x+3}} \right. \\\\\left \{ {{y=x+3} \atop {3x-x=3-6}} \right. \\\\\left \{ {{y=x+3} \atop {2x=-3\ /:2}} \right. \\\\\left \{ {{x=-1.5} \atop {y=-1.5+3}} \right. \\\\\left \{ {{x=-1.5} \atop {y=1.5}} \right.`