Answer :
Data:
• Red (R): 35
,• Yellow (Y): 39
,• He gives away (G): 18
,• Total final counters (T): unknown
Procedure:
[tex]\begin{gathered} T=R+Y-G \\ T=35+39-18 \\ T=74-18 \\ T=56 \end{gathered}[/tex]Answer: Robb has left 56 total counters.

Data:
• Red (R): 35
,• Yellow (Y): 39
,• He gives away (G): 18
,• Total final counters (T): unknown
Procedure:
[tex]\begin{gathered} T=R+Y-G \\ T=35+39-18 \\ T=74-18 \\ T=56 \end{gathered}[/tex]Answer: Robb has left 56 total counters.