Answer: The answer is 28.
Step-by-step explanation: 8a-y is our problem and we are given two variables, a and y. It is revealed that a=3 and y= -4. So our problem would now look like this: 8*3-(-4). Now see the two minuses (-) next to each other? We have to convert that into a plus (+) sign because two negatives make a positive. So our equation now looks like this: 8*3+4. Now, 8 times 3 (8*3) is equal to 24. Now our equation looks like this: 24+4. Add them together and the sum is 28.
Hope this helps!