Nathan has $322 worth of $11 and $13 stock shares. The number of $11 shares is seven more than twice the number of $13 shares. How many of each type of share does he have?
let x = the number of $11 shares
and y = the number of $13 shares
set up a system of equations
11x + 13y = 322
x = 2y + 7
substitute x in the first equation for the value in the second and solve