The first thing we do for this case is to define variables:
 x: hot dogs
 y: steak sandwiches
 We write the following system of equations:
 2.50x + 10y = 8470
 x + y = 985
 Resolving graphically we have:
 x = 184
 y = 801
 Note: see attached image for the solution.
 Answer:
 He sold:
 hot dogs = 184
 steak sandwiches = 801