6x-4y=54
-9x+2y=-6
substitution

The angle of a triangle are given as 6x,(x-3), and (3x+7). find x then find the measures of the angles

How to do this , and can some one explain

Each cookie sells for $0.50 sam spent $90 on baking supplies and each cookie cost $0.25 to make how many cookies does sam need to sell before making a profit formula: sales> cost