To isolate \( x \) in the equation \( 5x + 8 = 63 \), Randall will perform the operation of subtraction on the constant term 8. He will subtract 8 from both sides of the equation to eliminate the \( +8 \) term.
So, he will apply the subtraction to the value 8.
The operation looks like this:
\[ 5x + 8 - 8 = 63 - 8 \]
This simplifies to:
\[ 5x = 55 \]