Answer:
12
Step-by-step explanation:
Use the first two equations to solve for a and b.
multiply the second equation all the way through by -2
(-2)(a + 2b) = (-2)(7)
-2a -4b = -14 Add this to the first equation.
-2a - 4b = -14
+ 2a + 3b = 17
-b = 3 Multiply both sides by -1
b = -3 Plug -3 back into either of the 2 original equations to find a
a + 2b = 7
a + 2(-3) = 7
a - 6 = 7 Add 6 to both sides
a = 13
Now that we know a = -3 and b = 13, we can plug that into the third equation:
[tex]\frac{(3a + 5b)}{2}[/tex]
[tex]\frac{3(13) + 5(-3)}{2)}[/tex]
[tex]\frac{39 -15}{2}[/tex]
[tex]\frac{24}{2}[/tex] = 12
