Yolette charges $12.75 for a manicure and $19.50 for a pedicure. yolette did 7 manicures and 4 pedicures each day for 5 days. how much money did yolette earn altogether?

X+ y = 5 ; x - y =3 solve using linear combination

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters

Is experimental probibilty the same as the observed frequency in math? i need the answer asap!