From the problem, we have the expression :
[tex]4d+9-d-8[/tex]
Note that you can only combine terms if they have the same variables.
First thing to do is to regroup the terms with the same variables including the constants.
[tex]\begin{gathered} 4d+9-d-8 \\ \Rightarrow(4d-d)+(9-8) \\ \Rightarrow(3d)+(1) \\ \Rightarrow3d+1 \end{gathered}[/tex]
The answer is 3d + 1
