There's two ways, you can either multiply 11 and 7 to get 77 and then divide by 2, OR, you can divide 11 by 2 and get 5.5 and multiply that by 7, hope this makes sense, if you don't understand just comment and I'll explain it more :)
The Answer is A.
To solve the equation for x you need to find a, b and c of the quadratic then apply the quadratic formula resulting in that answer.
D and E —> substitute the x or y of the point given into the functions to test if it is correct
You had 12 the next day and the day after that you had 18
20% off means you paid only 80% of the original price.
0.8x=40
x=40÷0.8=50
so the original price is 50
