Simultaneous Equations

Simultaneous Equations is a equations with two unknown variable.
So, we would require two equation to solve these two variables.
Question :
Solve for x,y for below :
x + y = 7
2x - 3y = 4
Solution :
x + y = 7 ...... Equation (i)
2x - 3y = 4 ........ Equation(ii)
Multiply Equation (i) by 3
3x + 3y = 21......Equation(iii)
2x - 3y = 4.........Equation(ii)
Add Equation(iii) and (ii)
5x = 25
x = 25/5 = 5
Put x=5 in Equation (i)
5 + y = 7
y = 2
Answer x= 5 and y =2