Please answer all of these (i can’t put 30 points since there’s none so 25 points)

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

∆red ≅ ∆ by rule will give brainiest if possible

Ellen makes and sells bookmarks. she graphs the number of bookmarks sold compared to the total money earned. why is the rate of change for the function graphed to the left?