"line of symmetry" means a line where you could fold a shape in half and the two halves would match up perfectly. Or like where you could place a mirror and see the whole letter still looking perfect.
see image.
All the letters have one or two lines of symmetry except for S which has none.
The I is kind of debatable. It has at least one but posssibly two, depends on the font i guess.
<span>1/72 This is because the odds that, on two dice, two specific numbers get rolled is 1/36. But since the number has to be rolled on a specific dice, that doubles the fraction.</span>