What is the value of x in the equation 8x – 2y = 48, when y = 4?

8x - 2y = 48 
8x - 2 * 4 = 48
8x - 8 = 48
8x = 48 + 8
8x = 56
x = 56 / 8 
x = 7

Check : 8 * 7 - 2 * 4
             56 - 8
             48

We have an equation and we know one of the values of the variables.
Replace all variables that we know the values of. We know the value of y.
So, replace all y variables will the value of y.

Now the equation will look like 8x - 2(4) = 48

Solve for x.

When solving for a variable, you isolate that variable on one side of the equation and everything else on the opposite side of the equation.

We isolate the variable by undoing the operations done to the variable.

8x - 2(4) = 48
8x - 8 = 48 <--- -2 * 4 = -8
8x = 56      <--- Add 8 to both sides of the equation.
x = 7          <--- Divide both sides by 8

So, x is equal to 7.