1. Use substitution to solve the system of equations. -3x - y= 7
x + 2y= 6

2. Use substitution to solve the system of equations.
6x - 3y= -6
y= 2x + 2

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