Answer:
Alternative B - 7.
Step-by-step explanation:
Let
"a" be the number of sessions painted by a group of two students;
and
"b" be the number of sessions painted by a group of four students.
Since the number total of sessions is 23,
[tex]23=a+b[/tex]
Also, since the total of students is 76,
[tex]76=2\cdot a+4\cdot b[/tex]
We can isolate "a" in the first equation and substitute in the second to find b:
[tex]\begin{gathered} a+b=23 \\ a=23-b \end{gathered}[/tex][tex]\begin{gathered} 76=2\cdot(23-b)+4\cdot b \\ 76=46-2b+4b \\ 76-46=2b \\ 30=2b \\ b=\frac{30}{2} \\ b=15 \end{gathered}[/tex]
And, since a = 23 - b
[tex]\begin{gathered} a=23-15 \\ a=8 \end{gathered}[/tex]
Finally, how many more sessions are painted by 4-students group:
[tex]\begin{gathered} b-a \\ 15-8 \\ =7 \end{gathered}[/tex]
So, the 4-students group painted 7 more sessions.
Answer: Alternative B - 7.