Solve the following equations by the substitution method :
Step 1: Express one variable (say x) in terms of the other variable (say y) from one of the given equations:
Multiplying the equation throughout by 2:
Step 2: Substitute this value of x in the other equations to get a linear equation in y which can be solved:
Multiplying the equation throughout by 4:
Multiplying the equation throughout by 9:
Step 3: Substitute the values of y obtained in to get the values of x:
Hence, the value of .