To isolate \( x \) in the equation \( 5x + 8 = 63 \), Randall needs to first eliminate the constant term on the left side of the equation.
He will apply subtraction to the value \( 8 \).
So, he would subtract \( 8 \) from both sides of the equation:
\[ 5x + 8 - 8 = 63 - 8 \]
This simplifies to:
\[ 5x = 55 \]
Thus, he subtracts \( 8 \) from \( 63 \).