Substitute the values such as 2,3, and 6 into the expression A+2b-4c.
It would look like this: 2+ 2(3)-4(6)
You would then just do order of operations, 2(3) =6 , -4(6) = -24
So then the problem would just be rewritten as 2+6-24
Which would equal -16. Which would be your answer :)