Let
x------> represents the number of AA batteries
y------> represents the number of 9V batteries
we know that
The constraints are
[tex]x\geq 6[/tex]
[tex]x\leq 12[/tex]
so
[tex]6\leq x\leq 12[/tex] --------> inequality A
[tex]y\leq 15[/tex] --------> inequality B
[tex](x+y)\geq 20[/tex]
[tex](x+y)\leq 27[/tex]
so
[tex]20\leq (x+y) \leq 27[/tex]-----> inequality C
The solution of the system of inequalities is the shaded area in the attached figure
If a ordered pair meet all the constraints and make sense in the context of the situation, then the ordered pair is a solution of the system of inequalities
let's check each of the ordered pairs
case A) point [tex](7,13)[/tex]
[tex]x=7\ y=13[/tex]
Verify inequality A
[tex]6\leq 7\leq 12[/tex]--------> is true
Verify inequality B
[tex]13\leq 15[/tex] -------> is true
Verify inequality C
[tex]20\leq (7+13) \leq 27[/tex]
[tex]20\leq (20) \leq 27[/tex]------> is true
The ordered pair [tex](7,13)[/tex] meets all restrictions, therefore the ordered pair is a solution of the system of inequalities
case B) point [tex](8,11)[/tex]
[tex]x=8\ y=11[/tex]
Verify inequality A
[tex]6\leq 8\leq 12[/tex]--------> is true
Verify inequality B
[tex]11\leq 15[/tex] -------> is true
Verify inequality C
[tex]20\leq (8+11) \leq 27[/tex]
[tex]20\leq (19) \leq 27[/tex]------> is not true
The ordered pair [tex](8,11)[/tex] does not meet all the restrictions, therefore the ordered pair is not a solution of the system of inequalities.
case C) point [tex](10,16)[/tex]
[tex]x=10\ y=16[/tex]
Verify inequality A
[tex]6\leq 10\leq 12[/tex]--------> is true
Verify inequality B
[tex]16\leq 15[/tex] -------> is not true
Verify inequality C
[tex]20\leq (10+16) \leq 27[/tex]
[tex]20\leq (26) \leq 27[/tex]------> is not true
The ordered pair [tex](10,16)[/tex] does not meet all the restrictions, therefore the ordered pair is not a solution of the system of inequalities.
case D) point [tex](12,12)[/tex]
[tex]x=12\ y=12[/tex]
Verify inequality A
[tex]6\leq 12\leq 12[/tex]--------> is true
Verify inequality B
[tex]12\leq 15[/tex] -------> is true
Verify inequality C
[tex]20\leq (12+12) \leq 27[/tex]
[tex]20\leq (24) \leq 27[/tex]------> is true
The ordered pair [tex](12,12)[/tex] meets all restrictions, therefore the ordered pair is a solution of the system of inequalities
the answer is
[tex](7,13)[/tex]
[tex](12,12)[/tex]