Hello! I am not quite grasping the concept could you please walk me through?

When simplifying using addition and subtraction, you combine “like terms” by keeping the "like term" and adding or subtracting the numerical coefficients.
[tex]\begin{gathered} 8t+5+3t-3=8t+3t+5-3 \\ =(8+3)t+(5-3) \\ =11t+2 \end{gathered}[/tex]