Acars fuel tank can hold 20 gallons of gas total it is only half full you stop and buy 5 gallons of gas how full is he fuel tank after you buy gas

20÷2=10 ( gallons half full)

10+5=15 ( gallons you add)

The tank has 15 gallons and is 75% full

If you reflect over the y-axis, you're basically just folding the shape over the y-axis (vertical up/down line) which means if you were to look at the points, A-A' would share teh same y coordinate point but the x coordinate point would be inversed (become negative)

going through your choices
A. looks like its reflected over the x-axis
C looks like its reflected over the x-axis, then y-axis
D. looks like a translation from the 3rd quadrant to the 1st

B. is a reflection over the y-axis