Solve this simultanous equation x + y = 5 (1) and 4x + y = 14 (2)

When you solve these types of equations you basically want to get rid of one of the variables(that is x or y) and solve for one. So if you get rid of y you have to find the value of x.

Lets add them to get rid of the y

Multiply equation 1 by -1

-x -y = -5
4x +y =14
------------------
3x = 9

x=3

Now plug this value of x into any one of the equations to find y, lets pick x +y =5 because the numbers are smaller

3 + y =5

y = 5-3

y=2

x=3, y=2

Subtract equation 1 from equation 2 and solve:
4x + y = 14
- x + y = 5
----------------
3x - 0y = 9
3x = 9
x = 3

Now take x=3 and plug it into equation 1:

3 + y = 5
y = 5 - 3
y = 2

So,
x=3, y=2