Given that the solution of the system of equations {ax + 3Y = (A-1) / 2,3x-2y = 10 is also the solution of equation 9x + 4Y = 40, the value of a is obtained

Given that the solution of the system of equations {ax + 3Y = (A-1) / 2,3x-2y = 10 is also the solution of equation 9x + 4Y = 40, the value of a is obtained

Because the solution satisfies these three equations, it must satisfy 3x-2y = 10 and 9x + 4Y = 40
By solving these two equations, we can get: x = 4, y = 1
By substituting x = 4 and y = 1 into ax + 3Y = (A-1) / 2, we can get
4a+3=(a-1)/2
The solution is a = - 1