To find the value of x in the equation 4x + 8y = 40 when y = 8, we start by substituting 8 for y in the equation.
So, the equation becomes:
4x + 8(8) = 40
This simplifies to:
4x + 64 = 40
Next, we need to isolate 4x. We do this by subtracting 64 from both sides of the equation:
4x = 40 – 64
This further simplifies to:
4x = -24
Now, we divide both sides by 4 to solve for x:
x = -24 / 4
Thus, we find:
x = -6
In conclusion, when y is 8, the value of x is -6.