So, we have an equation with a variable (g), and they've given us the value of g to be -2. All we have to do at this stage is plug in the value of g into the equation.
-5g-6 (g=-2)
-5(-2)-6
10-6=4
Doing the math by plugging in -2, you would get your answer to be 4. Let me know if you see any errors, and if you have any further questions at all.
