Here you have a system of 2 equations and 2 unknowns. An easy way to solve this type is to isolate one of the variables.
12a + 2b = 8
2b = 8 - 12a
b =
b = 4 - 6a
Now plug 4 - 6a into equation 1 to solve for a.
a + 5(4 - 6a) = 19
a + 20 - 30a = 19
-29a = -1
a = 1/29 (answer)
Now plug a into the equation for b
b= 4 - 6(1/29)
b= 110/29 (answer)
12a + 2b = 8
2b = 8 - 12a
b =
b = 4 - 6a
Now plug 4 - 6a into equation 1 to solve for a.
a + 5(4 - 6a) = 19
a + 20 - 30a = 19
-29a = -1
a = 1/29 (answer)
Now plug a into the equation for b
b= 4 - 6(1/29)
b= 110/29 (answer)