option A and D
Explanation:[tex]\begin{gathered} \text{Given:} \\ 6f\text{ + 3} \end{gathered}[/tex]We need to check the options:
[tex]\begin{gathered} a)\text{ }6f\text{ + 7 - 4} \\ 7\text{ -4 = 3} \\ 6f\text{ + 7 - 4 = 6f + 3} \\ \text{option is right} \end{gathered}[/tex][tex]\begin{gathered} b)\text{ }6f\text{ - 3 not the same as 6f + 3 } \\ \text{(opton is wrong)} \end{gathered}[/tex][tex]\begin{gathered} c)\text{ }18f\text{ not the same as 6f + 3 } \\ \text{(option is wrong)} \end{gathered}[/tex][tex]\begin{gathered} d)\text{ }3f\text{ + 3f + 1 + 1 + 1 } \\ 3f\text{ + 3f = 6f} \\ 1\text{ + 1 + 1 = 3} \\ =\text{ 6f + 3} \\ \text{option is right} \end{gathered}[/tex][tex]\begin{gathered} e)\text{ }3f\text{ + 6 is not the same as 6f + 3} \\ \text{option is wrong} \end{gathered}[/tex]