To evaluate the expression 5 - 3(x - 1) when x = 7, we need to substitute the value of x, 7, wherever x is present in the expression. Substituting, our expression becomes:
5 - 3(7 - 1)
We now need to do PEMDAS, meaning that we have to simplify the parenthesis first. Doing this, we get:
5 -3(6)
Now wee have to do multiplication.
5 - 18
Now, the final step is to do subtraction.
-13
That means that when x = 7, this expression has a value of -13.