15. - 2 (a - 4) = 13

a=-22

Step-by-step explanation:

Multiply both sides of the negative equation by (-2) to get the equation:

a-4=13 (-2)

then simplify to get:

a-4=-26

then isolate the variable by addig 4 to both sides of the equation to get:

a=-26+4

simplify to get:

a=-22