Solve the system using elimination. 3x + 3y = –9 3x – 3y = 21

The 3y and -3y would cross out, so you would add the 3xs together and you’d get 6x, now you add -9 and 21 and get 12. You divide 6x by 12 and end up getting 2 for your x. Then you substitute the 2 in for an any of the equations to get the y value. Ex) instead of 3x-3y=-9 it would be 3(2)-3y=-9 and you would multiply 3 and 2 to get 6 and solve for y by adding 6 to both sides and then dividing by -3 and you should get -3 then divide by -3 and your y value is positive 1

Agc and bgd are vertical angles