I would change 6x+3y=21 to y=-2x+7.
You can isolate the y value by subtracting the x to the other side. All the numbers have 3 in common, so you need to divide all of them by 3. I would then substitute the new equation into the 2x-3y=-13, making it 2x-3(-2x+7)=-13
You wove the equation, and once you get your x value, you needles to substitute it in the equation: y=-2x+7
The final answers will be x=1 and y=5
