What fraction is equivalent of the repeating decimal 2.5

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

If f(x) =3x-2 and g(x) =2x+1 fins (f+ g) (x)

Asource of laser light sends rays ab and ac toward two opposite walls of a hall. the light rays strike the walls at points b and c, as shown below: what is the distance between the walls?